Paronychia

INTRODUCTION — Paronychia is an inflammation involving the lateral and proximal nail folds. It may be acute (lasting for less than six weeks) or chronic (lasting for six weeks or longer) [1]. Predisposing factors include overzealous manicuring, nail biting, picking at a hangnail, thumbsucking, ingrown nail, diabetes mellitus, and occupations in which the hands are frequently immersed in water [2]. Paronychia has also been reported as an adverse effect of several drugs, including antiretroviral agents [3,4], systemic retinoids, epidermal growth factor receptor (EGFR) inhibitors, and cytotoxic chemotherapy agents [5,6].

This topic will discuss the pathogenesis, clinical manifestations, and management of acute and chronic paronychia. Ingrown toenails and other nail disorders are discussed separately. (See "Ingrown nails" and "Overview of nail disorders" and "Nail psoriasis" and "Principles and overview of nail surgery" and "Nail avulsion and chemical matricectomy" and "Nail biopsy: Indications and techniques" and "Dermoscopy of nail pigmentations" and "Dermoscopy of nonpigmented nail lesions".)

ACUTE PARONYCHIA

Definition — Acute paronychia is an acute inflammatory process, with or without abscess formation, that involves the proximal and lateral nail folds and that has been present for less than six weeks [1,7].

Pathogenesis

Infectious agents — Acute paronychia is most commonly caused by the inoculation of pathogens present in the skin flora (eg, Staphylococcus aureus, Streptococcus pyogenes) into the periungual tissues by minor mechanical or chemical traumas that disrupt the nail fold barrier [7]. Other organisms that may be occasionally involved, especially in acute episodes occurring in patients with chronic paronychia, include Pseudomonas aeruginosa and other Gram-negative bacteria.

In digits exposed to oral flora, acute paronychia may be caused by either skin or oral flora. In this setting, organisms include both aerobic bacteria (such as streptococci, S. aureus, and Eikenella corrodens) and anaerobic bacteria (eg, Fusobacterium, Peptostreptococcus, Prevotella, Porphyromonas spp) [8,9].

Drugs — Acute paronychia may be an adverse effect of several drugs, including epidermal growth factor receptor (EGFR) inhibitors (eg, cetuximab, erlotinib, panitumumab, lapatinib), cytotoxic chemotherapy agents (eg, taxanes, capecitabine, methotrexate, doxorubicin) [5,6], systemic retinoids [10-12], and antiretroviral agents [4,13-15]. In patients treated with EGFR inhibitors, paronychia is thought to result from EGFR-induced changes in differentiation and migration of keratinocytes and decrease in keratinocyte proliferation and survival [5]. Although the periungual lesions are initially sterile, bacterial superinfection is common and may lead to abscess formation.

Predisposing factors — Common favoring factors for acute paronychia of the fingernails include manicuring, nail biting, thumbsucking, and picking at a hangnail. Acute paronychia of the toes occurs in most cases in association with ingrown toenails [16]. (See "Ingrown nails".)

Clinical presentation — Acute paronychia is characterized by the rapid onset of painful erythema and swelling of the proximal and lateral nail folds, usually in two to five days following a minor local trauma. A superficial abscess is frequently present (picture 1A-C). The infection may occasionally extend along the proximal nail fold to the opposite side of the nail, resulting in the so-called "runaround infection."

Paronychia usually involves one finger. Multiple nails can be involved in drug-induced paronychia.

Toenail paronychia is most often associated with ingrown toenail or retronychia (ingrowth of the nail plate into the proximal nail fold) [16]. It may also occur in patients with congenital malalignment of the great toenails [17]. (See "Ingrown nails" and "Overview of nail disorders", section on 'Retronychia'.)

Complications — In rare cases, the infection may spread to the underlying nail bed or to the pulp space (felon) (figure 1) [18]. Felon requires prompt surgical treatment with incision and drainage to prevent the development of osteomyelitis, permanent nail deformities, and ischemic necrosis of the fingertip [19]. (See "Overview of hand infections", section on 'Superficial hand infections'.)

Late complications of acute paronychia include dystrophic changes of the nail plate, such as transverse nail plate grooves (Beau lines) (picture 2), onychomadesis (detachment of the nail plate) (picture 3), and permanent nail dystrophy.

Diagnosis — The diagnosis of acute paronychia is usually straightforward, based upon a history of local minor trauma and the clinical finding of swollen, tender proximal or lateral nail folds, often associated with a purulent fluid collection (picture 1A, 1C-D). Usually, these findings have been present for less than six weeks. A digital pressure test has been suggested as a simple method to identify the presence and extent of a paronychial abscess [20]. A blanching appearing on the paronychium after applying a mild pressure to the volar aspect of the tip of the affected finger indicates the presence of an abscess.

Laboratory tests are usually not necessary for the diagnosis. However, in patients with severe infection and abscess, a pus culture should be obtained to guide antimicrobial therapy.

Differential diagnosis — The differential diagnosis of paronychia includes the following:

●Felon – Paronychia must be distinguished from felon, an infection of the digital pulp space (picture 4 and figure 2) characterized by severe pain, swelling, and erythema in the pad of the fingertip that is typically more dramatic than the onset of paronychia. (See "Overview of hand infections", section on 'Superficial hand infections'.)

●Herpetic whitlow – Acute onset is associated with vesicles, vesicopustules, severe edema, erythema, or pain (picture 5). The patient should be asked about exposure to herpes simplex virus (HSV). Tzanck staining of vesicles will demonstrate multinucleated giant cells. Immunofluorescence staining and viral culture can also be used to confirm HSV infection. (See "Epidemiology, clinical manifestations, and diagnosis of herpes simplex virus type 1 infection", section on 'Herpetic whitlow'.)

●Acrodermatitis continua of Hallopeau – Acrodermatitis continua of Hallopeau is a rare variant of pustular psoriasis characterized by a chronic, relapsing, inflammatory eruption with sterile pustules that primarily involves the distal fingers or toes, nail folds, and nail beds (picture 6) [21]. The initial presentation of acrodermatitis continua of Hallopeau may mimic acute paronychia; however, unlike acute paronychia, pustules are sterile. Nail destruction is a prominent feature of long-standing disease (picture 7). (See "Pustular psoriasis: Pathogenesis, clinical manifestations, and diagnosis", section on 'Acrodermatitis continua of Hallopeau'.)

●Proximal onychomycosis – Proximal subungual onychomycosis due to molds is typically associated with erythema, swelling of the proximal nail fold, and occasionally with purulent discharge (picture 8) [22]. (See "Onychomycosis: Epidemiology, clinical features, and diagnosis".)

●Green nail syndrome – Infection of the nail plate from P. aeruginosa, also called green nail syndrome or chloronychia, causes a nail plate blue-green discoloration (picture 9A-B). Prolonged exposure to water is a predisposing factor. In some cases, this condition may occur simultaneously with chronic paronychia [23]. (See "Pseudomonas aeruginosa skin and soft tissue infections", section on 'Green nail syndrome'.)

●Retronychia – A rare entity of multiple generations of nail plate growth backwards beneath the proximal nail fold (picture 10) [24]. (See "Overview of nail disorders", section on 'Retronychia'.)

●Pemphigus vulgaris – Acute paronychia is a relatively common clinical feature of pemphigus vulgaris [25-27]. (See "Pathogenesis, clinical manifestations, and diagnosis of pemphigus".)

Treatment — The treatment of acute paronychia includes local skin-care measures, topical or oral antibiotics, and surgical modalities, depending upon the severity of inflammation and presence or absence of abscess or associated ingrown toenail. There are no high-quality studies evaluating the use of oral versus topical antibiotics for uncomplicated paronychia or the use of oral antibiotics in addition to surgical incision and drainage for acute paronychia with abscess [28]. The approach to treatment is thus based upon clinical experience and limited evidence from observational studies (algorithm 1).

Paronychia without abscess — In patients with inflammation without abscess formation, treatment with topical antibiotics and warm water or antiseptic soaks (eg, chlorhexidine, povidone-iodine) multiple times per day is usually effective (algorithm 1) [29]. We typically instruct the patient to apply an antistaphylococcal antibiotic (eg, triple antibiotic ointment or mupirocin) after each warm soak. Warm soaks should last 10 to 15 minutes.

A single nonrandomized study compared the efficacy of a combination of topical fusidic acid plus betamethasone valerate with topical gentamycin in 20 patients with uncomplicated acute paronychia that did not require treatment with oral antibiotics [29]. Both treatments were effective in reducing pain, redness, and swelling.

Empiric oral antibiotic therapy may be needed in more severe cases that do not respond to topical treatment alone. An antistaphylococcal agent such as dicloxacillin (250 mg four times daily) or cephalexin (500 mg three to four times daily) is an appropriate first-line therapy. (See "Acute cellulitis and erysipelas in adults: Treatment", section on 'Without an indication for MRSA coverage'.)

In patients with risk factors for methicillin-resistant S. aureus (MRSA) colonization (table 1), oral agents that cover local strains of MRSA are a reasonable choice [30]. Options for empiric oral therapy with activity against MRSA include trimethoprim-sulfamethoxazole (one to two double-strength tablets twice daily), clindamycin (300 to 450 mg four times per day), or doxycycline (100 mg twice daily). (See "Acute cellulitis and erysipelas in adults: Treatment", section on 'With an indication for MRSA coverage'.)

For patients with a digit that has been exposed to oral flora (nail biting, finger sucking), antibiotic coverage should include S. aureus, E. corrodens, Haemophilus influenzae, and beta-lactamase-producing oral anaerobic bacteria (table 2). Considerations regarding coverage for MRSA are the same as those discussed above.

Paronychia with abscess — Acute paronychia with abscess formation is generally treated with incision and drainage (algorithm 1). Several surgical techniques have been described, although there is no consensus among experts on the best procedure or on the need for topical or systemic antibiotic therapy following the abscess drainage [28]. However, given the increasing frequency of MRSA infections, we suggest that a pus culture be obtained for all drained paronychias.

In a prospective study, 46 patients (26 with paronychia with abscess, 17 with paronychia and felon, and 3 with felon) were treated with incision and drainage alone without oral antibiotics [31]. Forty-five patients were healed without complications at 45 days. The authors concluded that for patients who are not at risk for infectious complications, postoperative antibiotic therapy is not warranted.

Incision and drainage is often performed by the insertion of a number 11 surgical blade under the affected cuticle margin, after appropriate local anesthesia (digital block or ethyl chloride spray) (see "Digital nerve block"). Extension of the incision along the lateral nail fold is indicated if the infection is unilateral. Incisions along both sides of the nail may be necessary for runaround abscess.

Another method that can be used when the abscess is superficially located is to use a large-gauge needle and run it (bevel down) along the nail fold and into the abscess. In one report, a 23 or 21 gauge needle was used to lift the nail fold off the nail plate, allowing passive oozing of pus [32]. This procedure did not require local anesthesia.

A partial nail plate removal is usually performed for the treatment of paronychia associated with ingrown toenail. However, a partial or complete nail plate removal may also be needed for patients with abscess extending to the nail bed.

After incision and drainage, frequent warm soaks will help to maintain the patency of the incision and assist wound drainage. Drainage alone is sufficient for many cases of paronychia with abscess formation [31].

However, for more severe cases or in immunosuppressed patients, we administer a course of oral antibiotics following incision and drainage of the abscess. Antibiotic treatment is typically given for five days. When available, culture and susceptibility results should be used to tailor antibiotic therapy.

The approach to selecting empiric antibiotic therapy is the same as for paronychia without abscess. (See 'Paronychia without abscess' above.)

Toenail paronychia — Acute paronychia of the toenails is usually associated with ingrowing nail or retronychia [16]. Treatment should be addressed to both the acute inflammation and the underlying condition. (See "Overview of nail disorders", section on 'Retronychia' and "Ingrown nails".)

Drug-induced paronychia — In most cases, drug-induced paronychia without superimposed infection improves or regresses with dose reduction or withdrawal of the offending agent [33]. In patients with paronychia induced by EGFR inhibitors, which is in most cases mild, some experts suggest treatment with topical antibiotics and potent topical corticosteroids while continuing EGFR inhibitors, with a temporary discontinuation of the offending drug limited to the most severe cases [34]. Other treatments that have been reported as beneficial in small studies include the gutter method (as used for ingrown nails) [35], red light-emitting diode [36], and a combination of topical beta blockers and topical antibiotics [37]. Topical timolol may also be beneficial for patients with periungual pyogenic granuloma complicating drug-induced paronychia [38,39]. (See "Pyogenic granuloma (lobular capillary hemangioma)".)

Preemptive therapy with oral doxycycline, topical corticosteroids, and moisturizers reduces the incidence of skin toxicities (including paronychia) associated with EGFR inhibitors [40]. (See "Acneiform eruption secondary to epidermal growth factor receptor (EGFR) and MEK inhibitors", section on 'Preemptive therapy'.)

Patients with clinical or laboratory evidence of secondary infection are treated with topical antiseptics and topical or systemic antibiotics as discussed previously. (See 'Paronychia without abscess' above and 'Paronychia with abscess' above.)

CHRONIC PARONYCHIA — Chronic paronychia is an inflammatory dermatosis involving the nail folds that has been present for more than six weeks [41]. It commonly occurs in individuals persistently exposed to environmental irritants and allergens (eg, wet work, foods, chemicals), such as food handlers, farmers, health care professionals, and domestic workers. Chronic paronychia may also be associated with inflammatory skin diseases, such as atopic dermatitis and psoriasis.

Pathogenesis — Chronic paronychia is considered to be an inflammatory response to repeated exposure to irritants or allergen [41]. The colonization by fungi and bacteria is thought to be a secondary occurrence rather than the initiating event. Although Candida spp is isolated from the proximal nail fold in 40 to 95 percent of patients with chronic paronychia, candidal infection may contribute to the persistence of the disease but should not be considered an etiologic factor, as eradication of the yeast does not cure the condition [1,42].

Clinical presentation — Chronic paronychia presents initially with edema and mild erythema of the proximal and lateral nail folds with loss of the cuticle (picture 11A). Over time, the nail folds become hypertrophic, with marked retraction of the proximal nail fold (picture 11B). These changes result in continued exposure of the periungual tissues and the matrix to irritants.

Dystrophic changes of the nail plate, such as ridging and Beau lines, are often present, due to disturbed nail growth; discolorations of the nail plate due to secondary bacterial or fungal infections are also common (picture 11A). Episodes of acute paronychia that exacerbate the swelling and erythema may occur.

Diagnosis — The diagnosis of chronic paronychia is usually clinical, based upon the characteristic clinical findings of hypertrophy and retraction of the proximal nail fold, loss of the cuticle, and nail dystrophy (picture 11A-B). A history of repeated exposure to wet work, irritant chemicals, or allergens further supports the clinical diagnosis. Patch testing may be indicated in patients with suspected allergic contact dermatitis. (See "Patch testing".)

A skin biopsy is generally not necessary for the diagnosis of chronic paronychia. However, in patients presenting with atypical clinical features (eg, ulceration, excessive inflammation or desquamation) and in patients with recalcitrant disease, a skin biopsy for histopathologic examination should be performed to rule out malignancy or other conditions mimicking chronic paronychia.

Differential diagnosis — Squamous cell carcinoma (SSC) and SSC in situ (Bowen disease) arising on the nail folds may mimic chronic paronychia [43]. The presentation is often that of a persistent eczematous eruption involving the periungual skin (picture 12) that does not improve with standard therapies [44,45]. Subungual hyperkeratosis may be an associated feature (picture 13). A skin biopsy can confirm the diagnosis. (See "Overview of nail disorders", section on 'Malignant tumors'.)

Recalcitrant chronic paronychia can rarely be the manifestation of cutaneous metastases of internal cancers [46,47], ungual leishmaniasis [48,49], and pyodermatitis-pyostomatitis vegetans associated with inflammatory bowel disease [43].

Treatment

General measures — Avoidance of environmental triggers is an essential component of treatment of chronic paronychia. Patients should be advised to keep their hands as dry as possible and to use gloves for all wet work. Given the possible association between chronic paronychia and eczema, patients with known contact allergies should also avoid irritant or allergen exposure.

First-line therapy — We suggest topical corticosteroids rather than topical or oral antifungals as a first-line therapy for chronic paronychia, in conjunction with the skin-protection measures described above. A high-potency topical corticosteroid (group 3 (table 3)) is applied once or twice daily for two to four weeks or until improvement is noted.

The use of topical corticosteroids rather than antifungal agents for the treatment of chronic paronychia is supported by the findings of a small, well-designed, randomized trial comparing topical corticosteroids with antifungal therapy [50]. In this study, 45 patients with chronic paronychia were randomly assigned to receive one of three treatments: oral itraconazole 200 mg, oral terbinafine 250 mg, or methylprednisolone aceponate 0.1% cream (a high-potency topical corticosteroid). Trial participants given oral medications used a placebo cream, and patients receiving methylprednisolone aceponate were given an oral placebo. Patients were treated for three weeks and then followed for six more weeks. Topical methylprednisolone therapy was associated with a significantly higher cure rate compared with systemic antifungal therapy (85 versus 49 percent of nails, respectively). Only 18 patients had Candida cultured from the proximal nail fold at the beginning of the study, and of these, Candida eradication was associated with clinical cure in only two.

The topical calcineurin inhibitor tacrolimus may be an alternative therapeutic option for patients who prefer not using topical corticosteroids. Topical tacrolimus 0.1% ointment was similar in efficacy to betamethasone 17-valerate 0.1% ointment and superior to placebo in one randomized, unblinded trial of 45 patients with chronic paronychia [51].

Refractory chronic paronychia — A surgical approach is reserved for patients with recalcitrant disease that failed to respond to medical treatments. Several techniques have been proposed [52]:

●The "en bloc excision" involves the removal of a crescent-shaped, full-thickness specimen of the proximal nail fold with a maximal width of 3 to 6 mm, with or without removal of the nail plate [53,54].

●In contrast with the en bloc excision, the "square flap technique" removes only the fibrotic tissue of the nail folds, preserving the epidermis and the underlying matrix [55]. In this technique, an incision is made on both sides of the proximal nail fold and a flap is created by making an incision parallel to the epidermis at the distal-thickened proximal nail fold. This incision runs underneath the fibrotic tissue but above the nail, which is used as a guide to avoid matrix damage. The flap is tilted backward, and the fibrotic tissue is removed with the scalpel blade. The primary closure is made with a simple interrupted suture.

●The "Swiss roll" technique has been proposed for both chronic paronychia and acute paronychia with runaround abscess [56]. In this technique, the nail fold is elevated by making an incision on either side and reflected proximally over a nonadherent dressing that is rolled up like a Swiss roll and fixed to the skin with two anchoring nonabsorbable sutures. The fold is kept open for 48 hours and, if the wound is clean, the sutures are removed and the proximal nail fold falls back to its original position and heals by second intention.

Prevention — Careful local skin care is advisable for the prevention of chronic paronychia. Patients should keep their hands and feet as dry as possible and not soak them in soapy water for prolonged periods of time without adequate protection. Nails should be cut carefully, and nail trauma or injury should be avoided.

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Ingrown toenail (The Basics)" and "Patient education: Paronychia (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Acute paronychia

•Definition – Acute paronychia is an acute inflammatory process that involves the proximal and lateral nail folds and that has been present for <6 weeks.

•Etiology and predisposing factors – Acute paronychia is most commonly caused by the inoculation of pathogens present in the skin flora (eg, Staphylococcus aureus, Streptococcus pyogenes) into the periungual tissues by minor mechanical or chemical traumas (eg, manicuring, nail biting, thumbsucking, picking at a hangnail). It may also be an adverse effect of several drugs, including epidermal growth factor receptor (EGFR) inhibitors, cytotoxic chemotherapy agents, systemic retinoids, and antiretroviral agents. (See 'Pathogenesis' above.)

•Clinical presentation – Acute paronychia is characterized by the rapid onset of painful erythema and swelling of the proximal and lateral nail folds. A superficial abscess is frequently present (picture 1A-C). (See 'Clinical presentation' above.)

•Diagnosis – The diagnosis is usually straightforward, based upon the clinical appearance and a history of a local minor trauma. Paronychia must be distinguished from felon, an infection of the digital pulp space (picture 4) characterized by severe pain and swelling limited to the soft tissue around the distal phalanx. (See 'Diagnosis' above and 'Differential diagnosis' above.)

•Treatment

-Acute paronychia without abscess – For patients with acute paronychia without abscess, we suggest initial treatment with warm water or antiseptic soaks (eg, chlorhexidine, povidone-iodine) plus topical antibiotics rather than oral antibiotic therapy (algorithm 1) (Grade 2C). A topical antistaphylococcal antibiotic (eg, triple antibiotic ointment or mupirocin) should be applied after each warm soak.

Empiric oral antibiotic therapy with an antistaphylococcal agent (eg, dicloxacillin or cephalexin) is reserved for more severe cases that do not respond to topical treatment. In patients with risk factors for methicillin-resistant Staphylococcus aureus (MRSA) colonization (table 1), empiric coverage for MRSA (eg, trimethoprim-sulfamethoxazole, clindamycin, or doxycycline) may be warranted. For patients with a digit that has been exposed to oral flora (nail biting, finger sucking), antibiotic coverage should include S. aureus, Eikenella corrodens, Haemophilus influenzae, and beta-lactamase-producing oral anaerobic bacteria (table 2). (See 'Paronychia without abscess' above.)

-Acute paronychia with abscess – Acute paronychia with abscess is treated with incision and drainage followed by frequent warm soaks to help to maintain the patency of the incision and assist wound drainage. Drainage alone is sufficient for most cases of paronychia with abscess. In severe cases or in immunosuppressed patients, we suggest an adjunctive empiric oral antibiotic (algorithm 1) (Grade 2C). The choice of empiric antibiotic is the same as for paronychia without abscess. When available, culture and susceptibility results should be used to tailor antibiotic therapy. (See 'Paronychia with abscess' above.)

●Chronic paronychia

•Pathogenesis – Chronic paronychia is a chronic inflammatory dermatosis involving the nail folds. It is caused by repeated exposure to irritants or allergen, with secondary colonization by fungi and bacteria. (See 'Chronic paronychia' above and 'Pathogenesis' above.)

•Clinical presentation – Common clinical features of chronic paronychia include periungual erythema and swelling, loss of the cuticle, and nail dystrophy. The cause of chronic paronychia may be multifactorial. (See 'Clinical presentation' above.)

●Treatment – Patients with chronic paronychia should be advised to keep their hands as dry as possible and to use gloves for all wet work. In addition to these general measures, we suggest topical corticosteroids rather than topical or oral antifungals as a first-line therapy (Grade 2B). A surgical approach is reserved for patients with recalcitrant disease that failed to respond to medical treatments. (See 'First-line therapy' above and 'Refractory chronic paronychia' above.)