Clinical features and diagnosis of bullous pemphigoid and mucous membrane pemphigoid

INTRODUCTION — Bullous pemphigoid and mucous membrane pemphigoid (MMP) are autoimmune blistering diseases that most commonly arise in older adults (picture 1A-F). These disorders are characterized by subepithelial blister formation and the deposition of immunoglobulins and complement within the epidermal and/or mucosal basement membrane zone. Historically, the term "cicatricial pemphigoid" also referred to MMP.

Although both bullous pemphigoid and MMP may affect skin and mucosa, the classical clinical findings in bullous pemphigoid are tense, fluid-filled bullae on skin, whereas the prevailing clinical feature in MMP is mucosal involvement. In MMP, inflamed and eroded mucosa is characteristic, involving any or all of the oral cavity, ocular conjunctiva, nose, pharynx, larynx, esophagus, anus, and genital mucous membranes.

The clinical features and diagnosis of bullous pemphigoid and MMP will be reviewed here (algorithm 1). The epidemiology, pathogenesis, and treatment of these disorders, as well as greater detail on the ocular form of MMP, are discussed separately.

●(See "Epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid".)

●(See "Management and prognosis of bullous pemphigoid".)

●(See "Management of mucous membrane pemphigoid".)

●(See "Ocular cicatricial pemphigoid".)

Pemphigoid gestationis, a rare form of pemphigoid associated with pregnancy, is reviewed separately.

●(See "Dermatoses of pregnancy", section on 'Pemphigoid gestationis'.)

CLINICAL FEATURES OF BULLOUS PEMPHIGOID

Clinical features — Important clinical features for bullous pemphigoid include signs and symptoms that may precede blister formation, blister morphology, and the distribution of skin involvement:

●Prodromal phase – A prodromal phase lasting weeks to months may precede the development of cutaneous bullae [1,2]. The prodromal phase may present with pruritic, eczematous, papular, or urticaria-like skin lesions (picture 1G) [3,4]. Some patients with bullous pemphigoid never develop blistering.

●Lesion morphology – When blisters develop, the classical lesion is a 1 to 3 cm, tense bulla on an erythematous, urticarial, or noninflammatory base, and blisters may be numerous and widespread (picture 1A-C) [5]. The tense quality of the bullae differentiates lesions of bullous pemphigoid from the flaccid bullae of pemphigus, of which the Nikolsky sign is a moderately sensitive, but highly specific, finding (picture 2A) [1,6]. (See "Pathogenesis, clinical manifestations, and diagnosis of pemphigus".)

Eventually, the bullae rupture, leaving moist erosions and crusts that resolve without scarring. When mainly erosions are present, it may be difficult to clinically distinguish bullous pemphigoid and pemphigus (picture 2B).

Associated pruritus is common and can be severe [7-9].

●Distribution – The trunk, extremity flexures, and axillary and inguinal folds are common sites for cutaneous involvement (picture 3A-C) [10]. Mucosal lesions are present in 10 to 30 percent of patients (picture 4) [1,2,5,11]. The oral mucosa is the most frequent location of mucosal involvement. Less frequently, bullous pemphigoid involves other mucosal sites, such as the larynx, genitals, and anus [11]. Nail changes may also develop [12,13].

Localized forms of bullous pemphigoid occur and account for up to 30 percent of cases [14]. Examples include disease limited to the lower legs (picture 1H) [14-18], anogenital region [19,20], peristomal skin [21,22], or sites of incidental or iatrogenic trauma (eg, radiation therapy) [23-29]. Disease that begins in localized areas may remain localized or may progress to generalized involvement [14,30].

Clinical variants — Clinical variants of bullous pemphigoid include nonbullous presentations, lichen planus pemphigoides, and other rare variants:

●Nonbullous presentations – Nonbullous presentations of bullous pemphigoid include eczematous, urticarial, and prurigo-like (pemphigoid nodularis) presentations, as well as bullous pemphigoid presenting as pruritus without any primary skin lesions (pruritic nonbullous pemphigoid, bullous pemphigoid as pruritus in older adults). In such cases, the diagnosis is based upon consistent laboratory findings [2,31-34]. (See 'Confirmatory testing' below.)

It is estimated that approximately 20 percent of patients with bullous pemphigoid present with nonbullous manifestations [35]. In a retrospective study of 69 patients with nonbullous pemphigoid, the most common presentations included pruritic papules or nodules (37 percent of patients) and pruritus without primary skin lesions (22 percent of patients) [34]. Progression to blistering disease eventually occurs in some patients.

●Lichen planus pemphigoides – Lichen planus pemphigoides is a rare variant of bullous pemphigoid. It is postulated that the cellular inflammatory process, which occurs at the basement membrane zone in lichen planus, results in exposure of basement membrane zone antigens, leading to subsequent development of basement membrane zone antibodies [36].

Patients with lichen planus pemphigoides typically present with bullae in sites of previously normal-appearing skin or mucosa. The bullae usually appear weeks to months after the onset of lichen planus [3]. (See "Lichen planus", section on 'Overlap syndromes'.)

●Other rare variants – Examples of rare variants include:

•Pemphigoid vegetans – Verruciform plaques in intertriginous areas [37,38]

•Dyshidrosiform pemphigoid – Palmar and/or plantar skin involvement (resembling dyshidrotic eczema), often hemorrhagic (picture 1I) [39,40]

•Vesicular bullous pemphigoid – Lesions resembling dermatitis herpetiformis [41]

•Bullous pemphigoid occurring in association with transient palmoplantar keratoderma [42] (see "Palmoplantar keratoderma", section on 'Acquired palmoplantar keratoderma')

CLINICAL FEATURES OF MUCOUS MEMBRANE PEMPHIGOID — MMP represents a group of heterogeneous, chronic, subepithelial, blistering disorders that primarily affect mucosal surfaces [43]. Mucosal involvement, with or without associated cutaneous involvement, characterizes MMP.

Some authors also consider cases of linear IgA bullous dermatosis and epidermolysis bullosa acquisita that primarily involve the mucous membranes as forms of MMP [43]. However, we view these diagnoses as distinct entities. (See "Linear IgA bullous dermatosis" and "Epidermolysis bullosa acquisita".)

Mucosal features — Characteristic clinical features of MMP include mucosal erosions and scarring:

●Lesion morphology and distribution – MMP typically presents as relapsing and remitting, mucosal inflammation and erosions (picture 1D-F). The detection of intact vesicles or bullae on mucosa is uncommon. Compared with the mucosal lesions of pemphigus (picture 2C), pain associated with oral MMP lesions is usually less intense [2].

The oral cavity is the most common site of involvement. In a report that summarized the sites of involvement in 457 patients with MMP, the frequency of affected sites was as follows [44]:

•Oral mucosa (85 percent)

•Ocular conjunctiva (64 percent)

•Skin (24 percent)

•Pharynx (19 percent)

•External genitalia (17 percent)

•Nasal mucosa (15 percent)

•Larynx (8 percent)

•Anus (4 percent)

•Esophagus (4 percent)

In the oral cavity, the gingival and buccal mucosae are most commonly affected. Gingival disease usually manifests as a desquamative or erosive gingivitis (picture 1D) and, in mild cases, may manifest only with gingival erythema and edema [45].

●Scarring – Scarring is a common consequence of MMP that distinguishes this variant from mucosal involvement in bullous pemphigoid, which typically does not scar. Reticulated, white striations representing mucosal fibrosis are often present at sites of healed lesions, and functional limitations secondary to scarring may occur [2,45]. As examples, MMP involving the ocular mucosa can lead to symblepharon, ankyloblepharon, and eventual blindness, and progressive laryngeal and tracheal involvement can result in asphyxiation (picture 5) [45]. (See "Ocular cicatricial pemphigoid", section on 'Clinical manifestations'.)

Cutaneous features — Cutaneous involvement in patients with MMP typically involves the scalp, face, or upper trunk. Blistering lesions resemble those seen in bullous pemphigoid but, similar to mucosal lesions of MMP, often heal with scarring.

ASSOCIATED DISORDERS — Patients with bullous pemphigoid often have multiple comorbidities [46-53]. In a case-control study that included 105 patients with bullous pemphigoid and 315 matched controls, patients with bullous pemphigoid were more likely to have two or more other chronic diseases (84 versus 65 percent) [46]. In particular, multiple studies have evaluated associations between bullous pemphigoid and neurologic disorders and between MMP and malignancy.

Neurologic disorders — Examples of neurologic disorders that may be associated with bullous pemphigoid include dementia, Parkinson disease, bipolar disorder, stroke, and multiple sclerosis:

●Evidence – Associations between bullous pemphigoid and neurologic disorders have been reported in observational studies and case reports [47,53-65]. In a hospital-based, prospective, case-control study of 201 patients with bullous pemphigoid and 345 matched controls, dementia, Parkinson disease, and unipolar or bipolar disorder were among the identified independent risk factors for this disease [56]. In addition, a population-based, case-control study of 868 patients with bullous pemphigoid and more than 3400 controls found that patients with pre-existing diagnoses of dementia, Parkinson disease, or stroke were significantly more likely to develop bullous pemphigoid [55]. Further, a case-control study with more than 5000 patients with multiple sclerosis and over 26,000 controls supported an association of bullous pemphigoid and this disease [66]. Neurologic cancers are included in the range of neurologic disorders associated with bullous pemphigoid [67].

●Rationale – Homology between bullous pemphigoid antigens in the skin and neuronal antigens in the central nervous system has been proposed as a cause for the observed link between bullous pemphigoid and neurologic disease, along with a genetic predisposition [68-72]. However, further studies are necessary to explore the relationship between these disorders. (See "Epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid", section on 'Epitope spreading'.)

●Patient evaluation – Each patient visit should include assessment of neurologic signs and symptoms in the review of systems, with referral to neurology if positive findings are identified.

Malignancy — MMP can occur in association with malignancy. A relatively strong association exists between MMP with antibodies directed against laminin 332 (previously known as laminin 5 and epiligrin) and internal malignancy (figure 1). The relationship between bullous pemphigoid and malignancy is less clear:

●Mucous membrane pemphigoid:

•Evidence – In a cohort of 35 patients with anti-laminin 332 MMP (diagnosed with immunoprecipitation), 10 patients (29 percent) developed solid organ malignancies, 7 of which were diagnosed within 14 months after a diagnosis of MMP [73]. Occurrences of non-Hodgkin lymphoma and cutaneous T cell lymphoma have also been reported in individual patients with anti-laminin 332 MMP [74]. In a series of 55 patients with anti-laminin 332 MMP, 14 percent had associated malignancies of various tissues, some with multiple tumors [75].

There may also be an increased risk for malignancy in patients with other forms of MMP, although the degree of risk is unclear. In a case series of 22 patients with MMP from a single institution, four patients (18 percent) had an associated cancer [76]. All four patients were negative for laminin 332 antibodies.

•Rationale – The pathophysiologic relationship of MMP with antibodies against laminin 332 to cancer is unknown. However, expression of laminin 332 has been detected in malignant cells, and laminin 332 appears to be capable of promoting tumor cell growth, invasion, and metastasis [74,77].

•Recognition and evaluation of patients at risk – The clinical manifestations of MMP in patients with laminin 332 antibodies are similar to the features of MMP with other antibody profiles. Therefore, clinical examination cannot reliably distinguish anti-laminin 332 MMP from other forms of MMP.

Since diagnostic laboratory testing for laminin 332 antibodies is not commercially available, suspicion for laminin 332 is primarily based upon serologic findings. Although not exclusive to laminin 332 MMP, the detection of serum antibodies bound to the dermal side of basement membrane zone-split (salt-split) skin suggests the possibility of this diagnosis. (See 'Indirect immunofluorescence assay' below.)

Until definitive testing for laminin 332 antibodies becomes available, we advise that patients with MMP in whom serum studies reveal antibodies bound to the dermal side of basement membrane zone-split skin undergo age- and sex-appropriate cancer screening. Additional evaluation for malignancy should be performed as indicated based upon a review of symptoms, physical examination, and the results of age-appropriate screening.

●Bullous pemphigoid – While some studies support an association, others have failed to find a significant increase in malignancy risk, attributing occurrences of malignancy to age rather than bullous pemphigoid [53,78,79]. A systematic review and meta-analysis of observational studies did not find an association of bullous pemphigoid with malignancy overall but found an association between bullous pemphigoid and hematologic malignancies [80]. Another meta-analysis of studies assessing the association between bullous pemphigoid and malignancy found a greater event rate of malignancy in patients with bullous pemphigoid compared with controls and a slightly lower event rate for malignancy in Asian studies compared with European studies [81].

In our practice, we evaluate young and middle-aged patients with bullous pemphigoid for underlying malignancy particularly when they present with severe or refractory disease, present with symptoms or signs in organ systems other than skin, or if there is a family history of genetically associated malignancy. Our typical approach is to ensure age- and sex-appropriate cancer screening. Additional evaluation for malignancy is based upon a review of symptoms, physical examination, and the results of age-appropriate screening.

DISEASE COURSE — Bullous pemphigoid is a chronic disorder characterized by exacerbations and remissions over the course of months to years. However, in some patients, the disease is self-limited, resulting in disease remissions within a few years. (See "Management and prognosis of bullous pemphigoid", section on 'Prognosis'.)

In the absence of treatment, MMP is usually a chronic, progressive disease that results in functionally limiting or, in some cases (eg, those with airway involvement), life-threatening disease [45]. The clinical course and prognosis of ocular MMP is reviewed in greater detail separately. (See "Ocular cicatricial pemphigoid", section on 'Clinical manifestations' and "Ocular cicatricial pemphigoid", section on 'Prognosis and cessation of therapy'.)

DIAGNOSIS — Although clinical findings may strongly suggest bullous pemphigoid or MMP, other disorders present with similar mucocutaneous lesions, and nonbullous or other less typical presentations can occur (table 1). Thus, confirmation of the diagnosis requires the careful interpretation of both clinical and laboratory findings. (See 'Differential diagnosis' below.)

Recognition of suggestive clinical findings — Bullous pemphigoid or MMP should be strongly considered when patients over the age of 60 years present with one or more of the following clinical features:

●Blistering skin disease characterized by the presence of tense blisters and erosions that occur without another identifiable cause

●Desquamative gingivitis or mucositis involving oral, ocular, nasal, genital, anal, pharyngeal, laryngeal, and/or esophageal mucosae

●Unexplained pruritus; pruritic, eczematous eruptions; or urticarial plaques

The possibility of bullous pemphigoid or MMP should also be considered in the evaluation of younger adults, children, and infants with suggestive signs or symptoms in the absence of another identifiable cause (picture 1J) [82-84]. (See "Epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid", section on 'Epidemiology' and 'Clinical features of bullous pemphigoid' above and 'Clinical features of mucous membrane pemphigoid' above.)

Laboratory assessment is indicated when clinical findings suggest bullous pemphigoid or MMP. (See 'Confirmatory testing' below.)

Confirmatory testing — The principal studies used in the evaluation of patients with lesions suspicious for bullous pemphigoid or MMP include biopsy for routine histopathologic examination, biopsy for direct immunofluorescence (DIF) microscopy, and serum tests to detect circulating anti-basement membrane zone antibodies (indirect immunofluorescence [IIF] assay and enzyme-linked immunosorbent assay [ELISA]) (table 2).

Test selection — An algorithm depicting the approach to the diagnosis of patients with clinical findings suspicious for bullous pemphigoid or MMP is provided (algorithm 1).

Initial tests — In patients with clinical findings suggestive of bullous pemphigoid or MMP, we begin the laboratory assessment by obtaining both of the following (algorithm 1):

●Lesional tissue specimen for routine (fixed tissue) histopathology

●Perilesional tissue specimen for DIF examinations

Routine histopathologic examination provides diagnostic support through detection of pathologic findings that are consistent or inconsistent with bullous pemphigoid or MMP. DIF detects characteristic immunoglobulin and complement deposition within the skin or mucous membrane. (See 'Tissue biopsy' below and 'Routine histopathologic examination' below and 'Direct immunofluorescence' below.)

Subsequent tests — We perform serum testing to detect circulating anti-basement membrane zone antibodies in all patients with histopathologic and DIF findings consistent with bullous pemphigoid or MMP. We also perform serum testing when strong clinical suspicion for bullous pemphigoid or MMP remains despite histopathologic or DIF findings that are not entirely consistent with bullous pemphigoid or MMP (algorithm 1).

We typically obtain both of the following types of serum tests:

●IIF assays on human basement membrane zone-split skin and monkey esophagus substrates

●Bullous pemphigoid antigen 180 (BP180) and bullous pemphigoid antigen 230 (BP230) immunoglobulin G (IgG) antibody ELISAs

IIF plays an important role in diagnosis, as it allows for the differentiation of bullous pemphigoid from other autoimmune blistering diseases, enables presumptive identification of patients at risk for malignancy-associated laminin 332 MMP, and supports a diagnosis when DIF is negative or not feasible (algorithm 1) [35,85,86].

ELISA testing provides additional diagnostic support and may have value for assessing the response to treatment. ELISA testing may be more sensitive than IIF for the diagnosis of bullous pemphigoid and MMP but can be negative in some patients with bullous pemphigoid or MMP because of the limited display of potential target epitopes in the assays (algorithm 1) [85,86]. (See 'Indirect immunofluorescence assay' below and 'Enzyme-linked immunosorbent assay' below.)

A diagnostic accuracy study supports routine performance of both DIF and IIF for the standard-of-care diagnostic evaluation of bullous pemphigoid. In an analysis of 1125 patients with suspected bullous pemphigoid in which 343 received a pemphigoid diagnosis, DIF was the most sensitive diagnostic test (sensitivity of 88.3 percent, 95% CI 84.5-91.3 percent and specificity of 99.2 percent, 95% CI 98.3-99.7 percent), and IIF on human basement membrane zone-split (salt-split) skin was less sensitive but highly specific (sensitivity of 77 percent, 95% CI 72.2-81.1 and specificity of 99.9 percent, 95% CI 99.3-100 percent) [35]. IIF complemented DIF, exhibiting positivity in most cases of bullous pemphigoid with negative DIF findings. Based upon the study results, the authors proposed at least two of the following three characteristics as minimal diagnostic criteria:

●Pruritus and/or predominant, cutaneous blisters

●Linear IgG and/or C3 deposits by DIF on a skin biopsy specimen

●Positive epidermal (roof) side IgG basement membrane zone antibody localization on split skin substrate by IIF with a serum specimen

Tissue biopsy — Lesional biopsies for routine histopathologic examination and perilesional skin biopsies for DIF can support a diagnosis of bullous pemphigoid or MMP. (See 'Test selection' above.)

General principles — Separate specimens are optimal for routine histopathologic examination and DIF because of differences in the preferred biopsy location (lesional versus perilesional) and tissue handling (preservation in formalin versus specialized transport medium) (table 2). We typically obtain two 4 mm punch biopsies. Careful splitting of a 5 or 6 mm punch biopsy specimen or a shave biopsy specimen into lesional and perilesional specimens is an alternative. (See "Skin biopsy techniques", section on 'Punch biopsy' and "Approach to the patient with cutaneous blisters", section on 'Skin biopsy'.)

If only one small specimen can be obtained, the preferred test to perform is DIF.

Routine histopathologic examination — Histopathologic examination supports a diagnosis of bullous pemphigoid or MMP through the detection of consistent histopathologic findings but is not sufficient for diagnosis:

●Biopsy technique – Skin biopsies for routine histopathologic examination (ie, hematoxylin and eosin [H&E] staining) should be taken from lesional tissue, preferably of an intact vesicle or the edge of an intact bulla (table 2). The specimen should include the blister edge and the immediately adjacent tissue. If blisters are absent, the lesional biopsy may be taken from other involved sites of inflammation (eg, urticarial or eczematous lesions or inflamed areas of mucosa).

Care should be taken to avoid excessive torsion and crushing, which may alter tissue cleavage planes and increase the difficulty of pathologic interpretation.

Obtaining a mucosal lesional specimen is not always possible in MMP because affected mucosa is friable and easily erodes. A biopsy for DIF should still be performed in these cases [87]. (See 'General principles' above and 'Direct immunofluorescence' below.)

●Specimen transport – Specimens obtained for H&E are placed in formalin for processing.

●Biopsy interpretation – Common histopathologic findings in cutaneous lesions of bullous pemphigoid include [1]:

•Eosinophilic spongiosis (particularly in early lesions) (picture 6)

•Subepidermal blister formation (often with numerous eosinophils within cleft) (picture 7)

•A superficial, dermal, inflammatory cell infiltrate of variable intensity with lymphocytes, eosinophils, and neutrophils (picture 6)

The histopathologic findings in nonbullous pemphigoid are often nonspecific. A dermal, perivascular infiltrate with eosinophils is a common finding [34].

Histopathologic examination of mucosal lesions of MMP shows epithelial-subepithelial cleavage and a mixed, submucosal, inflammatory cell infiltrate composed of lymphocytes, histiocytes, neutrophils, and eosinophils [45]. Additional findings may include plasma cell infiltration and subepidermal fibrosis; the latter is a finding consistent with the scarring nature of MMP [45].

Direct immunofluorescence — Direct immunofluorescence (DIF) is a highly sensitive, supportive diagnostic test for pemphigoid [35,86-88]. The procedure utilizes labeled antibodies to detect immunoglobulin binding and complement deposits in tissue. DIF is a more sensitive test for the diagnosis of bullous pemphigoid and MMP than serum IIF or ELISA tests [35,86,87] (see "Approach to the patient with cutaneous blisters", section on 'Direct immunofluorescence'):

●Biopsy technique – In contrast to biopsy specimens for H&E histopathologic evaluation, biopsy specimens for DIF should be obtained from perilesional, not lesional, skin (table 2). Different definitions have been used for "perilesional" skin, including an erythematous or urticarial area or normal-appearing skin adjacent to (but not including) a blister:

•Cutaneous biopsies – For cutaneous biopsies, we typically aim to biopsy an erythematous or urticarial area adjacent to a blister [89]. Newly inflamed skin unassociated with a blister is also acceptable in patients with findings suggestive of the prodromal phase of bullous pemphigoid or of nonbullous pemphigoid.

Whether biopsying perilesional, inflamed skin is preferred over perilesional, normal-appearing skin is unclear. One prospective study that compared DIF findings in skin taken from erythematous skin adjacent to a blister and normal-appearing skin within 2 cm of an erythematous area in 43 patients with autoimmune blistering disease (including 40 with bullous pemphigoid) did not find a significant difference in DIF findings [90].

Various explanations have been put forth for discordant DIF results, especially with respect to false-negative findings. Increased potential for false-negative findings in distal extremities has been disputed [91-95]. DIF may be a less useful diagnostic test in localized bullous pemphigoid than in generalized disease [93].

•Mucosal biopsies – On mucosa, tissue immediately adjacent to an erosion can be friable. A tissue specimen from normal-appearing mucosa several millimeters away from the edge of a lesion can be obtained. Intact mucosa with epithelium attached to subepithelium is optimal for DIF.

●Specimen transport – The tissue specimen for DIF should not be placed in formalin. Rather, the specimen should be promptly placed in a transport medium compatible with the performance of immunofluorescence studies, such as Michel's medium or Zeus medium (table 2). Specimens for DIF should be transported promptly to an immunodermatology laboratory for receipt within seven days of obtaining the specimen; transport medium does not preserve a specimen indefinitely.

Some immunodermatology laboratories will also accept specimens transported on normal, saline-soaked gauze (provided they are received during laboratory working hours within six hours of obtaining them; sooner is better) or specimens that are flash frozen and transported on dry ice (table 2).

●Interpretation – The classic DIF findings in bullous pemphigoid and MMP include [45,86,88,96]:

•Bullous pemphigoid – Linear IgG and/or linear C3 staining along the basement membrane zone is present in more than 90 percent of cases (picture 8A-C). Less intense linear basement membrane zone staining for immunoglobulin M (IgM), immunoglobulin A (IgA), and/or immunoglobulin E (IgE) may be present. Linear IgM with linear C3 is rare [97]. DIF is less likely to be characteristically positive in nonbullous pemphigoid, supporting performance of both DIF and serologic studies [34,35]. (See 'Test selection' above.)

•Mucous membrane pemphigoid – Linear IgG, linear IgA, and/or linear C3 staining along the basement membrane zone is detected in approximately 70 to 100 percent of cases. Repeat DIF testing on more than one biopsy specimen may be of value for patients with suspected MMP who test negative; multiple or repeated biopsies increase the sensitivity of DIF for the diagnosis of MMP (algorithm 1) [98]. Linear IgE basement membrane zone staining can be detected in specimens from some patients [99].

Additional clues for diagnosis may be provided by analysis of the linear pattern of basement membrane zone antibody staining detected in DIF. Whereas an n-serrated pattern has been associated with bullous pemphigoid, MMP, anti-p200 pemphigoid, and linear IgA dermatosis (picture 8C), a u-serrated pattern has been described in epidermolysis bullosa acquisita and bullous systemic lupus erythematosus (picture 9) [100,101]. A true linear pattern is commonly observed along with the characteristic n-serrated and u-serrated patterns in all of these immunobullous diseases [100,101].

A modified DIF technique has been described utilizing basement membrane zone-split perilesional skin or mucosa from patients with suspected pemphigoid. Theoretically, this allows for more precise localization of antibody binding within the epithelial basement membrane zone of diseased tissue and, therefore, additional information for diagnosis [102]. However, the accuracy and reliability of this technically difficult testing procedure have not been established. In particular, basement membrane zone separation is often difficult and may be variable with inflamed skin and frequently is impossible to perform on mucosal specimens. Performing IIF with the patient's serum on basement membrane zone-split skin substrate is a more practical test. (See 'Indirect immunofluorescence assay' below.)

Serum tests — IIF and ELISA testing can support a diagnosis of bullous pemphigoid or MMP. (See 'Test selection' above.)

Indirect immunofluorescence assay — Indirect immunofluorescence (IIF) testing is used to detect circulating basement membrane zone antibodies (picture 10A):

●Technique – To perform this test, the patient's serum is overlaid on an epithelial tissue substrate, incubated, and then stained for fluorescent detection of antibodies (table 2). Typically, both monkey esophagus and human skin that is artificially split at the level of the lower lamina lucida of the basement membrane zone are utilized. The human skin is split using prolonged exposure (48 to 72 hours) to 1 M sodium chloride (salt-split skin) or short exposure (30 minutes) to ethylenediaminetetraacetic acid (EDTA). (See "Approach to the patient with cutaneous blisters", section on 'Indirect immunofluorescence'.)

●Interpretation – IIF findings supportive of bullous pemphigoid or MMP consist of IgG antibody localization along the basement membrane zone. The location of antibody deposition on basement membrane zone-split skin provides information that may be helpful for distinguishing bullous pemphigoid from other autoimmune skin diseases and for identifying patients with MMP at risk for malignancy-associated anti-laminin 332 MMP:

•Role in distinguishing autoimmune blistering diseases – Monkey esophagus is a useful substrate because it can broadly categorize autoimmune diseases based on antibody staining patterns.

IIF with a basement membrane zone-split skin substrate aids in distinguishing among certain subepithelial immunobullous diseases because the test allows for localization of antibody deposition within the basement membrane zone. Specimens from patients with bullous pemphigoid typically demonstrate antibody localized to the epidermal side (roof) of basement membrane zone-split skin, whereas in specimens from patients with epidermolysis bullosa acquisita, bullous lupus erythematosus, anti-laminin 332 pemphigoid, and anti-p200 (laminin gamma-1) pemphigoid, antibodies typically localize to the dermal side (picture 10A-B).

Among the autoimmune subepithelial immunobullous diseases, anti-p200 pemphigoid may be the most common cause of antibody deposition on the dermal side of split skin. In a German study of 141 serum specimens demonstrating autoantibody binding to the dermal side of split skin, 115 sera showed reactivity against p200 or laminin gamma-1 [103]. Combined epidermal-dermal staining patterns on basement membrane zone-split skin may be occasionally found in bullous pemphigoid and bullous lupus erythematosus (picture 11).

•Identification of patients at risk for laminin 332 pemphigoid – In MMP, basement membrane zone-split skin IIF is particularly useful for recognizing patients at risk for malignancy-associated laminin 332 MMP. In this condition, antibodies are found along the dermal side of the split [104,105].

Specific testing to confirm a diagnosis of anti-laminin 332 MMP remains limited to specialized centers and research settings [106]. Additional studies are needed to validate detection of antibodies with an IIF assay to recombinant laminin 332 [107]. (See 'Malignancy' above and 'Differential diagnosis' below.)

•Diagnostic value – IIF is a highly specific test for bullous pemphigoid [35,86]. In a retrospective study in which 313 patients with bullous pemphigoid were compared with 488 controls, the specificities of IIF on rabbit esophagus, IIF on monkey esophagus, and IIF on human salt-split skin for diagnosis were 96.5, 97.1, and 100 percent, respectively [86]. The sensitivities of these tests for diagnosis were 73.2, 73.3, and 72 percent, respectively. DIF had a similar specificity but was more sensitive. The specificity of DIF was 98 percent, and the sensitivity of DIF was 90.8 percent.

In early studies of MMP, IIF was positive in fewer than one-third of patients [45]. However, the use of human basement membrane zone-split skin and/or concentrated serum may increase the likelihood of detecting circulating antibodies [45,108,109]. In one series of eight patients with MMP, IIF on basement membrane zone-split skin was positive in 50 percent [108]. A larger series of 67 patients found that IIF on a basement membrane zone-split skin substrate yielded positive antibodies in 84 percent of patients [109].

Enzyme-linked immunosorbent assay — The identification of increased circulating IgG antibodies against BP180 and BP230 in patients with bullous pemphigoid and MMP has led to the use of adjunctive, antigen-specific serologic testing for these basement membrane zone antigens in the diagnosis of these disorders (figure 1). The most common technique used for this purpose is enzyme-linked immunosorbent assay (ELISA) (see "Epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid", section on 'Bullous pemphigoid'):

●Technique – ELISAs for bullous pemphigoid antibodies are commercially available. This testing detects circulating IgG that reacts with type XVII collagen or BP180 (specifically, the NC16A domain of BP180, which is the most common antigenic target, also known as bullous pemphigoid antigen 2 [BPAg2]) and with BP230 (specifically, fused antigenic targets from the N-terminal domain, central rod domain, and C-terminal domain of human BP230 and that is also known as bullous pemphigoid antigen 1 [BPAg1]).

●Interpretation:

•Bullous pemphigoid – ELISA for antibodies to the BP180 NC16A domain is useful for baseline information in the diagnosis of bullous pemphigoid. Studies have documented sensitivity and specificity of 72 to 90 percent and 90 to 99 percent, respectively [86,110-112]. Since IgG BP180 NC16A antibody levels also correlate with disease activity [113], many clinicians (including ourselves) utilize ELISA testing, not only to support the diagnosis of bullous pemphigoid but also as a measure of the response to therapy. (See "Management and prognosis of bullous pemphigoid", section on 'Assessing response to therapy'.)

ELISA for BP230 antibodies is less likely to be positive in bullous pemphigoid than ELISA testing for BP180 antibodies [86,110,114]. In a retrospective study that evaluated ELISA results in 190 patients with bullous pemphigoid, the sensitivity and specificity of the assay for BP230 were 61 and 96 percent, respectively, compared with 79 and 90 percent, respectively, for BP180 [110]. Moreover, combined testing for BP180 and BP230 antibodies was only slightly more sensitive than BP180 alone; the sensitivity and specificity of conjoint testing were 87 and 88 percent, respectively. Although this finding suggests that testing for BP230 should be reserved for patients who test negatively for BP180, immunodermatology laboratories, including ours, test for antibodies to both antigens in diagnostic panels for bullous pemphigoid [110]. We have observed a subset of pemphigoid patients who have strong epidermal pattern basement membrane zone IgG antibodies by IIF and relatively high levels of IgG BP230 antibodies by ELISA but normal IgG BP180 antibody levels. (See "Epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid", section on 'Pathogenesis'.)

Patients with bullous pemphigoid in whom BP180 and BP230 ELISA testing is negative may have antibodies to epitopes of BP180 or BP230 that are not recognized by commercial ELISA tests or may have antibodies to basement membrane zone antigens other than BP180 and BP230. In support of this observation, a study of 51 patients with clinical, histopathologic, and DIF findings consistent with bullous pemphigoid identified four patients (8 percent) in whom ELISA for BP180 NC16A was negative, three of whom also had negative ELISA for BP230 [115]. Despite the negative ELISA for BP180, further analysis by immunoblot revealed strong reactivity to BP180 epitopes outside of NC16A in all four patients, and IIF on basement membrane zone-split skin was positive in three of the four ELISA BP180-negative patients. A negative ELISA for BP180 NC16A domain in bullous pemphigoid may be associated with milder clinical manifestations [116].

The detection of BP180 and/or BP230 antibodies in serum does not definitively confirm a diagnosis of bullous pemphigoid. Correlation of ELISA findings with IIF and/or DIF is necessary for reducing the risk for misdiagnosing the disease, as demonstrated in a study that assessed overlap in positivity of DIF, IIF, ELISA, and immunoblotting in patients with bullous pemphigoid [35]. In one series of 337 people without bullous pemphigoid, 25 (7 percent) tested positively for one or both BP180 and BP230 autoantibodies via ELISA [117]. In another series at the same institution, 208 patients with BP180 or BP230 antibodies detected via ELISA and negative DIF for pemphigoid were assigned a wide variety of clinical diagnoses, including dermatitis as the most common diagnosis (72 patients [35 percent]) [118]. Bullous pemphigoid was the working clinical diagnosis in only 20 patients (10 percent) based upon review of the clinical presentation, positive IIF test results, and increased BP180 and BP230 antibody levels.

•Mucous membrane pemphigoid – MMP may present with autoantibodies directed against a variety of antigens, including BP180, BP230, laminin 332 (previously known as epiligrin and laminin 5), alpha-6 beta-4 integrin, and type VII collagen (figure 1) [43,119-123]. Limited sensitivity of ELISA testing for BP180 and BP230 antibodies in the diagnosis of MMP prevents the sole use of such testing.

The reliability of ELISA testing may differ among patients with MMP. Pooled data analysis in a systematic review of studies reporting autoantibody profiles of patients with MMP who had positive immunoblot or immunoprecipitation to the NC16A domain of BP180 found the sensitivity and specificity of ELISA using both NC16A and C-terminal epitope portions of BP180 to be 73 and 94 percent, respectively [123]. However, among patients with IgG reactivity against the C-terminal domain of BP180 on immunoblot or immunoprecipitation, the sensitivity and specificity of ELISA testing were 43 and 56 percent, respectively.

Antigen-specific testing of serum for basement membrane zone antibodies other than BP180 and BP230 is primarily performed in research laboratories, limiting the value of this testing mode in the MMP population. However, additional tests may be available in the future. Additional studies are necessary to confirm the findings of a retrospective study of 154 patients with MMP that associated the detection of laminin 332 antibodies via a novel ELISA with a greater likelihood for severe disease [119]. Further study is also necessary to clarify whether the detection of salivary IgA and IgG antibodies to BP180 NC16A by ELISA is a useful diagnostic biomarker for MMP [124]. (See "Epidemiology and pathogenesis of bullous pemphigoid and mucous membrane pemphigoid", section on 'Mucous membrane pemphigoid'.)

Other tests — Other techniques that have been utilized for the detection of antibodies in bullous pemphigoid include immunoblotting and immunoprecipitation. However, these tests are technically demanding and generally are not utilized in the clinical setting [1,85].

OTHER LABORATORY FINDINGS — Peripheral blood eosinophilia is common in patients with bullous pemphigoid but is not a diagnostic finding [125,126]. Increased interleukin (IL) 5, a critical Th2 cytokine in eosinophil production and activation, has been observed in peripheral blood and blister fluid in patients with bullous pemphigoid but has not been systematically studied [127,128]. Increased serum IgE levels are also commonly found [129,130].

DIFFERENTIAL DIAGNOSIS — The clinical findings in bullous pemphigoid and MMP may resemble a variety of other diseases, including other variants of pemphigoid and additional blistering or nonblistering diseases (table 1).

Other pemphigoid variants — Examples of pemphigoid variants in the differential diagnosis of bullous pemphigoid and MMP include pemphigoid gestationis, anti-p200 pemphigoid, and Brunsting-Perry pemphigoid.

Pemphigoid gestationis — Pemphigoid gestationis is an autoimmune subepidermal blistering disorder that develops during pregnancy and the postpartum period. Patients typically develop intensely pruritic papules, urticarial plaques, vesicles, and bullae that begin on the abdomen prior to spreading to other areas [131,132]. The face and mucous membranes are usually spared.

Like bullous pemphigoid, patients with pemphigoid gestationis have circulating BP180 antibodies that are detected by enzyme-linked immunosorbent assay (ELISA) [133]. On direct immunofluorescence (DIF), complement deposition predominates at the basement membrane zone. Pemphigoid gestationis is discussed in greater detail elsewhere. (See "Dermatoses of pregnancy", section on 'Pemphigoid gestationis'.)

Anti-p200 (laminin gamma-1) pemphigoid — Anti-p200 pemphigoid, also known as anti-laminin gamma-1 pemphigoid, is a variant of pemphigoid that is characterized by antibodies to a 200 kilodalton (kD) component of the dermal-epidermal junction. Indirect immunofluorescence (IIF) on basement membrane zone-split skin demonstrates dermal localization of basement membrane zone antibodies [134]. The antigenic target, in most cases, is the gamma-1 subunit of laminin 311 (previously known as laminin 6). (See 'Indirect immunofluorescence assay' above.)

Patients with this type of pemphigoid are usually younger than those with bullous pemphigoid but present with similar clinical features. In one series of 29 patients with this disorder, 25 patients were male, and the mean age was 61 years [135]. Additionally, 14 patients had coexistent psoriasis. In another series of 12 patients, tense, acral blisters and mucosal involvement were characteristic clinical features along with pruritus, and no patients had psoriasis [136].

Specific testing to confirm the presence of antibodies to p200, or particularly to laminin gamma-1, remains limited to specialized centers and research settings [137]. As a result, it is likely that patients with this form of pemphigoid are erroneously diagnosed with bullous pemphigoid or epidermolysis bullosa acquisita based on DIF findings [136]. Anti-p200 pemphigoid is one of the few diagnoses indicated by IIF testing that detects serum IgG basement membrane zone antibodies bound to the dermal side of split skin substrate; other examples include epidermolysis bullosa acquisita, bullous lupus, and anti-laminin 332 pemphigoid. Techniques that have been used to specifically identify p200 antibodies include immunoblot with human dermal extract, ELISA to laminin gamma-1, IIF on skin substrates deficient in type VII collagen and laminin 332, and localization of collagen type IV to the floor of blistering skin [136,138].

Brunsting-Perry pemphigoid — Brunsting-Perry pemphigoid is a cicatricial (scarring) form of pemphigoid that most commonly occurs in older males. Affected patients develop subepidermal blisters localized to the head or neck (picture 12). A variety of basement membrane zone antibodies have been detected in this variant [139-141].

Cutaneous lesions — Examples of other disorders in the differential diagnosis for patients with cutaneous lesions include (table 1 and algorithm 1):

●Urticaria and eczematous dermatitis – The prodromal-phase lesions of bullous pemphigoid may resemble the erythematous and edematous plaques of urticaria or the erythematous papules or plaques of eczematous dermatitis. Unlike true urticaria, the lesions of bullous pemphigoid are not transient. DIF studies of biopsy specimens are useful for distinguishing both of these disorders from bullous pemphigoid. (See "New-onset urticaria" and "Atopic dermatitis (eczema): Pathogenesis, clinical manifestations, and diagnosis".)

●Skin-predominant epidermolysis bullosa acquisita – Epidermolysis bullosa acquisita is a rare disorder characterized by subepidermal blister formation involving the skin and mucous membranes (picture 13). Unlike bullous pemphigoid, IIF on basement membrane zone-split skin demonstrates serum antibody bound to the dermal side of the split, and residual scarring and milia are common. Specific ELISA testing for antibodies to type VII collagen is useful for making this diagnosis. (See "Epidermolysis bullosa acquisita".)

●Pemphigus – Pemphigus is a group of autoimmune blistering disorders characterized by autoantibodies directed against epithelial cell surface antigens (also known as intercellular substance [ICS] antigens). The flaccid nature of blisters in pemphigus contrasts with the tense, subepidermal bullae in pemphigoid (picture 2A-C). DIF studies are essential for diagnosis. Several pemphigus variants exist, including paraneoplastic pemphigus (picture 2D), which may show basement membrane zone antibodies in addition to cell surface antibodies. (See "Paraneoplastic pemphigus" and "Pathogenesis, clinical manifestations, and diagnosis of pemphigus".)

●Linear IgA disease – Linear IgA disease, which includes linear IgA bullous dermatosis and chronic bullous disease of childhood, is an autoimmune subepithelial blistering disorder that usually presents with annular and grouped, tense vesicles arising on inflamed skin (picture 14). The skin lesions are often described as resembling a cluster of jewels. Mucosal sites may also be affected. The DIF finding of linear IgA antibody staining at the basement membrane zone in a perilesional skin biopsy specimen is essential for this diagnosis. (See "Linear IgA bullous dermatosis".)

●Dermatitis herpetiformis – Intensely pruritic, inflammatory papules, vesicles, or crusts with a predilection for the elbows, knees, and buttocks are characteristic of dermatitis herpetiformis, another autoimmune subepidermal blistering disorder (picture 15). The histopathologic finding of neutrophilic microabscesses in dermal papillary tips by hematoxylin and eosin (H&E) and the immunohistopathologic detection of granular and/or fibrillar IgA deposits in the papillary dermis by DIF are consistent with this diagnosis. (See "Dermatitis herpetiformis".)

●Bullous lupus erythematosus – Bullous systemic lupus erythematosus is a rare disorder. The development of subepidermal blisters with neutrophilic infiltrates in a patient with systemic lupus erythematosus suggests this disease. (See "Overview of cutaneous lupus erythematosus", section on 'Bullous cutaneous lupus erythematosus'.)

Mucosal lesions — Examples of other causes of mucosal erosions that must be distinguished from those associated with MMP and bullous pemphigoid include pemphigus variants (picture 2C-D), linear IgA bullous dermatosis or epidermolysis bullosa acquisita with mucosal involvement, oral and genital mucosal lichen planus (picture 16A-B), erythema multiforme (picture 17A-B), Stevens-Johnson syndrome (picture 18), HIV-associated mucosal lesions, Behçet syndrome, and aphthous ulcers (picture 19) [43]. (See "Paraneoplastic pemphigus" and "Linear IgA bullous dermatosis" and "Epidermolysis bullosa acquisita" and "Oral lichen planus: Pathogenesis, clinical features, and diagnosis" and "Erythema multiforme: Pathogenesis, clinical features, and diagnosis" and "Stevens-Johnson syndrome and toxic epidermal necrolysis: Pathogenesis, clinical manifestations, and diagnosis" and "Clinical manifestations and diagnosis of Behçet syndrome" and "Oral lesions", section on 'Erosive, ulcerative, and bullous lesions' and "Pathogenesis, clinical manifestations, and diagnosis of pemphigus".)

A broader differential diagnosis for oral or vulvar erosions, ulcers, and bullae is reviewed in detail separately. (See "Oral lesions", section on 'Erosive, ulcerative, and bullous lesions' and "Vulvar lesions: Differential diagnosis of vesicles, bullae, erosions, and ulcers".)

The differential diagnosis for ocular involvement is reviewed separately. (See "Ocular cicatricial pemphigoid", section on 'Differential diagnosis'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Bullous pemphigoid".)

SUMMARY AND RECOMMENDATIONS

●Bullous pemphigoid and mucous membrane pemphigoid (MMP) are uncommon autoimmune subepithelial blistering disorders that affect skin and mucous membranes. (See 'Introduction' above.)

●Features of bullous pemphigoid:

•The onset of blistering lesions in bullous pemphigoid is frequently preceded by a prodromal phase characterized by pruritic, inflammatory plaques that resemble eczematous dermatitis or urticaria. Once the bullous phase develops, patients exhibit multiple tense, 1 to 3 cm bullae as well as erosions and crusts at sites of ruptured bullae (picture 1A-C, 1G-J, 3A-C). The lesions of bullous pemphigoid usually heal without scarring. Nonblistering forms of bullous pemphigoid can occur. (See 'Clinical features of bullous pemphigoid' above.)

•The trunk and extremities are typically involved in bullous pemphigoid; localized presentations may also occur. Mucosal disease is present in 10 to 30 percent of patients (picture 4). (See 'Clinical features of bullous pemphigoid' above.)

●Features of mucous membrane pemphigoid:

•MMP most commonly presents as desquamative gingivitis or erosions of the oral mucosa. Other potential sites of mucosal involvement include the ocular conjunctiva, skin, pharynx, genitalia, nasal mucosa, larynx, anus, and esophagus (picture 1D-F). (See 'Clinical features of mucous membrane pemphigoid' above and "Ocular cicatricial pemphigoid", section on 'Clinical manifestations'.)

•Unlike bullous pemphigoid, lesions of MMP tend to scar. Scarring may result in serious functional impairment. (See 'Clinical features of mucous membrane pemphigoid' above.)

•Patients with the anti-laminin 332 (previously known as anti-laminin 5 or anti-epiligrin) form of MMP may have an increased risk for internal malignancy. An evaluation for associated malignancy should be performed in patients with immunohistopathologic findings that suggest this disorder. Specific testing for antibodies against laminin 332 is not yet widely available. (See 'Malignancy' above.)

●Diagnosis:

•The evaluation of patients with clinical findings suggestive of bullous pemphigoid or MMP begins with obtaining skin or mucous membrane biopsy specimens from both lesional tissue for hematoxylin and eosin (H&E; light microscopic histopathology) and perilesional tissue for direct immunofluorescence (DIF) (algorithm 1). DIF is highly sensitive for the diagnosis and demonstrates characteristic linear basement membrane zone antibody localization in almost all patients with bullous pemphigoid and the majority of patients with MMP (picture 8A-C). (See 'Tissue biopsy' above.)

•Serologic studies to detect circulating basement membrane zone antibodies by indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA) are also useful for the diagnosis of bullous pemphigoid and MMP. Both DIF and serologic studies should be performed as part of the diagnostic evaluation (picture 10A and algorithm 1). (See 'Indirect immunofluorescence assay' above and 'Enzyme-linked immunosorbent assay' above.)

•The differential diagnosis of bullous pemphigoid and MMP is broad (table 1). The possibility of other pemphigoid disorders, other blistering disorders, and nonbullous diseases must be considered. (See 'Differential diagnosis' above.)