Chronic granulomatous disease: Pathogenesis, clinical manifestations, and diagnosis

INTRODUCTION — Chronic granulomatous disease (CGD) is a genetically heterogeneous condition characterized by recurrent, life-threatening bacterial and fungal infections and granuloma formation. CGD is caused by defects in the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex, which constitutes the phagocyte oxidase (phox). These genetic defects result in the inability of phagocytes (neutrophils, monocytes, and macrophages) to destroy certain microbes. The diagnosis is made by neutrophil function testing for superoxide production (nitroblue tetrazolium reduction or dihydrorhodamine [DHR] 123 flow cytometry assay). The exact molecular defect is determined by genotyping.

Infections in patients with CGD are generally caused by catalase-positive microorganisms (most bacterial and all fungal pathogens are catalase positive), but catalase is neither necessary nor sufficient for pathogenicity in CGD. The frequent sites of infection are the lung, skin, lymph nodes, and liver. Inflammatory complications such as the formation of granulomata are especially problematic in the lungs and the gastrointestinal and genitourinary tracts. Colitis associated with CGD occurs in 30 to 40 percent of all patients with CGD regardless of residual superoxide production and genotype [1].

This topic reviews the pathogenesis, clinical manifestations, and diagnosis of CGD. The treatment and prognosis of CGD, as well as an overview of primary disorders of phagocyte function, are discussed separately. (See "Chronic granulomatous disease: Treatment and prognosis" and "Primary disorders of phagocyte number and/or function: An overview".)

EPIDEMIOLOGY — The frequency of CGD in the United States is approximately 1:200,000 live births [2]. The disease primarily affects males since over 50 percent of the pathogenic variants are X linked. Rates are almost identical across ethnic and racial groups, with approximately one-third of the X-linked pathogenic variants occurring de novo. However, in cultures in which consanguineous marriage is common, the autosomal recessive forms of CGD are more common than X-linked forms, and overall incidence rates may be higher [3].

CGD may present at any time from infancy to late adulthood, but the majority of patients are diagnosed as toddlers and children before the age of five years. In several series, the median age at diagnosis was 2.5 to 3 years of age [4-8]. A growing number of patients are diagnosed in later childhood or adulthood due in part to recognition of milder cases of autosomal recessive CGD, as well as delayed diagnosis in some patients. Diagnosis may also be delayed because of newer, potent antimicrobials that inadvertently treat many CGD-associated infections, postponing diagnosis until more severe infections indicate CGD as the underlying cause. X-linked CGD tends to have an earlier onset and be more severe than the most common autosomal recessive form, p47phox deficiency [2].

PATHOGENESIS — Phagocytes use nicotinamide adenine dinucleotide phosphate (NADPH) oxidase to generate reactive species of oxygen. CGD arises from pathogenic variants that result in the loss or functional inactivation of one of the six proteins required to make the NADPH oxidase complex. All of these proteins are necessary for the proper generation of superoxide. (See 'Genetic defects' below.)

The fully assembled NADPH oxidase is a five-protein complex. In the basal state, it exists as two components [9]:

●The membrane-bound heterodimer, called cytochrome b-245 or cytochrome b588, that is composed of gp91phox and p22phox and is embedded in the walls of secondary granules

●Proteins in the cytosol (p47phox, p67phox, and p40phox)

The assembly of the cytochrome is dependent upon a sixth protein that stabilizes the other five in the membrane of the endoplasmic reticulum. This protein is called essential for reactive oxygen species (EROS), encoded by cytochrome b-245 chaperone 1 (CYBC1). The absence of this protein can also cause CGD [10].

Activation and assembly of the functional oxidase also requires the participation of Rac2, a small guanosine triphosphate (GTP)-binding protein, and Rap1, a small GTPase.

Neutrophil priming — Neutrophils exist in one of three states: quiescent, activated, or primed. Primed neutrophils are poised to undergo an exaggerated respiratory burst or secretory response when specific receptors are triggered. (See 'Respiratory burst' below.)

Three main types of agonists are capable of priming neutrophils:

●Inflammatory mediators that are chemotactic

●Serum immunoglobulin and complement

●Inflammatory cytokines and growth factors such as tumor necrosis factor (TNF) alpha, lipopolysaccharide (LPS), peptidoglycan, granulocyte monocyte colony-stimulating factor (GM-CSF), granulocyte colony stimulation factor (G-CSF), substance P, orthovanadate, and interleukin (IL) 1

Priming may be achieved rapidly, over a few minutes, or more slowly, over 30 minutes, depending upon the nature of the stimulus. The primed state is transient, lasting up to several hours.

Activation of NADPH oxidase — The cytosolic components p47phox and p67phox are phosphorylated and bind tightly together after cellular activation is initiated by phagocytosis of microbes. In association with p40phox and Rac2, these proteins combine with the membrane-bound cytochrome complex (gp91phox and p22phox) to form the intact nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (figure 1) [9].

The source of reducing equivalents for the respiratory burst oxidase and the glutathione detoxification pathway is NADPH [11-14]. This compound is replenished from NADP by glucose-6-phosphate dehydrogenase (G6PD) through the hexose monophosphate shunt.

Respiratory burst — After the NADPH oxidase has formed, an electron is then taken from NADPH and donated to molecular oxygen, leading to the formation of superoxide. This is converted to hydrogen peroxide spontaneously or enzymatically by superoxide dismutase. In the final step, hydrogen peroxide reacts with superoxide anion, forming a highly reactive hydroxyl radical that is converted to hypochlorous acid in the presence of myeloperoxidase and chlorine in the neutrophil phagosome (figure 1). The rapid consumption of oxygen and production of superoxide and its metabolites is referred to as the "respiratory burst." Phagocyte production of reactive oxygen species (ROS) leads to potassium and proton influx into the phagolysosome, leading to activation of granule proteases, including elastase and cathepsin G. These proteases are responsible for the destruction of ingested (phagocytosed) microorganisms. Thus, superoxide acts as an intracellular-activating molecule in addition to a direct microbicidal molecule as previously thought [15-18]. This model also explains why patients with myeloperoxidase deficiency (MPO) do not develop the same infections as patients with CGD.

Innate immune receptors — Foreign material, such as bacteria, fungi, and parasites, display molecules that are not seen in higher organisms. Termed pathogen-associated molecular patterns (PAMPs), these molecular components of microorganisms are recognized by receptors globally referred to as pattern recognition receptors that include Toll-like receptors (TLRs). Patients with CGD, compared with the general population of patients with bacterial pneumonia, express lower levels of several neutrophil receptors, including TLRs (TLR5 and TLR9), complement receptors (CD11b, CD18, and CD35), and a chemokine receptor (CXCR1). In contrast, patients with pneumonia who do not have CGD generally have higher than normal expression levels of these proteins. Decreased expression results in impaired neutrophil activation (TLR5), phagocytosis (CD11b/CD18), and chemotaxis (CXCR1). Levels of expression of TLR5 and CD18 may correlate with CGD disease severity [19].

Neutrophil extracellular traps — Neutrophils can continue to participate in antimicrobial activity even after they undergo apoptosis. During neutrophil cell death, the nuclei swell, chromatin dissolves, and large strands of decondensed deoxyribonucleic acid (DNA) extrude from the cell, carrying with them proteins from cytosol, granules, and histones from the nuclei themselves [20,21]. These neutrophil extracellular traps (NETs) entangle and may contribute to the extracellular killing of bacteria and fungi [21,22]. NET formation is probably enhanced by hydrogen peroxide, and therefore patients with CGD do not form normal NETs [22-24].

Enhanced inflammation — Several different mechanisms may be involved in the enhanced inflammation seen in patients with CGD.

Inflammatory mediators — Defective production of ROS leads to increased expression of nuclear factor (NF) kappa-B-regulated inflammatory genes [25]. Higher levels of inflammatory mediators are expressed in monocytes from patients with X-linked CGD without acute infection compared with controls. A similar increase in transcription of antiinflammatory mediators is not seen.

Inflammasome activation — ROS dampen inflammasome activation in healthy individuals. This inhibition is impaired in patients with CGD [26-28].

Efferocytosis — Efferocytosis is the process by which apoptotic inflammatory cells are recognized and removed by phagocytes. Impaired efferocytosis has been demonstrated in macrophages in a mouse model of CGD [29] and in monocyte-derived macrophages from patients with CGD [30]. Defects in efferocytosis are suspected to contribute to the granulomatous inflammation seen in CGD. Treatment with pioglitazone restores efferocytosis, but it remains to be seen whether this therapy can alter the immune and inflammatory defects seen in CGD in vivo [31].

GENETIC DEFECTS — Pathogenic variants in the genes for the six proteins (gp91phox, p47phox, p22phox, p67phox, p40phox, and essential for reactive oxygen species [EROS]) that are required to make the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex account for all of the known cases of CGD. There are one X-linked and five autosomal recessive forms of CGD [2]:

●The gene for gp91phox is encoded by cytochrome b-245, beta subunit (CYBB), located at chromosome Xp21.1. Defects in this gene cause X-linked CGD (MIM #306400), which accounts for approximately 65 to 70 percent of cases in the United States and Europe [32]. Missense or splicing mutations may be associated with some low levels of residual superoxide production. Patients with these pathogenic variants generally have better survival than those with nonsense or deletion mutations that leave no residual superoxide production [33].

●The second membrane component, p22phox, is encoded by cytochrome b-245, alpha subunit (CYBA), located at chromosome 16q24. Defects in this gene cause an autosomal recessive CGD (MIM #233690), which accounts for less than 5 percent of cases [32].

●The cytosolic factor p47phox is encoded by neutrophil cytosolic factor 1 (NCF1), located at chromosome 7q11.23 (MIM #233700). Defects in this gene account for approximately 25 percent of North American cases. Approximately 80 percent of p47phox deficiency is due to a GT (guanine-thymine) deletion in exon 2 that is associated with residual superoxide production [34].

●The cytosolic factor, p67phox, is encoded by neutrophil cytosolic factor 2 (NCF2), located at chromosome 1q25 (MIM #233710). Defects in NCF2 account for less than 5 percent of cases [35].

●The cytosolic factor, p40phox, is encoded by neutrophil cytosolic factor 4 (NCF4), located at chromosome 22a13.1 (MIM #601488). Recessive defects in NCF4 cause a mildly impaired respiratory burst activity (may appear normal on standard neutrophil dihydrorhodamine 123 [DHR] testing) but severe inflammatory bowel disease (IBD) [36,37].

●The assembly of the cytochrome complex occurs in the endoplasmic reticulum and is dependent upon EROS (encoded by cytochrome b-245 chaperone 1 [CYBC1]), located at chromosome 17q25.3. A handful of patients with CGD due to autosomal recessive pathogenic variants in CYBC1 (MIM #618334) have been identified [10,38].

Neutrophil immunodeficiency syndrome, a syndrome with some overlap with CGD in terms of superoxide production but also with distinct neutrophil chemotaxis defects and T cell dysfunction [39], is caused by a dominant-negative pathogenic variant in the Ras-related C3 botulinum toxin substrate 2 (RAC2) gene. Patients with dominant-negative variants in RAC2 may have impaired superoxide production, impaired chemotaxis and adhesion, low T cell receptor excision circles (TRECs), severe bacterial infections, and poor wound healing [40,41]. In contrast, dominant activating RAC2 variants cause excessive superoxide production with impaired neutrophil migration and severe T and B cell lymphopenia [42].

The large majority of the identified pathogenic variants in the phagocyte oxidase (phox) proteins result in complete or nearly complete absence of the protein. A normal amount of a nonfunctioning or hypofunctioning protein results from the other (minority) variants. The superscripts ⁺, ^-, and ⁰ have been used to indicate normal, decreased, or absent protein levels, respectively [9].

A macrophage-specific defect in gp91phox expression appears to predispose more to localized Bacillus Calmette-Guérin (BCG) infection and tuberculosis (TB) than the other infections typically seen in CGD [43]. (See "Mendelian susceptibility to mycobacterial diseases: Specific defects".)

CLINICAL MANIFESTATIONS — Patients with CGD usually present with recurrent or severe infections caused by bacteria or fungi. Other presenting features include growth failure, abnormal wound healing, diarrhea, and granulomatous dermatitis. Patients with CGD may have hepatomegaly, splenomegaly, or lymphadenitis [44] on physical examination.

Infections — Patients with CGD typically experience repeated infections caused by bacterial and fungal pathogens. However, CGD patients may exhibit few clinical signs and symptoms, despite the presence of significant infection. Response to viral infections is normal in patients with CGD. Lower residual superoxide production is associated with a higher risk of severe infections and a higher mortality, but it does not affect the rates of CGD-related colitis [45].

Bacterial infections in CGD tend to be symptomatic and are typically associated with fever, pleuritic chest pain, and inflammatory marker (eg, C-reactive protein [CRP]) elevation but only mildly elevated leukocyte counts [46]. In contrast, fungal infections are typically associated with little to no fever and lower leukocytosis and are therefore more difficult to recognize clinically. Fungal infections are often detected either at asymptomatic stages on routine screening for infections [47] or at an advanced stage. As an example, patients with fungal osteomyelitis may not be diagnosed until later stages of disease, when they have multiorgan involvement [48].

Sites of infection — The most common sites of infection are the lung, skin, lymph nodes, and liver [2].

The types of serious infections most often seen (in descending order of frequency) include [45,49]:

●Pneumonia

●Abscesses (skin, tissue, organs)

●Suppurative adenitis

●Osteomyelitis

●Bacteremia/fungemia

●Superficial skin infections (cellulitis/impetigo)

Pneumonia is the most common pulmonary infection, but patients may also have lung abscesses, empyema, and hilar lymphadenopathy. In contrast to what occurs in neutropenic patients, fungal pneumonias do not generally cavitate in CGD, whereas Nocardia infections do. In a series of adults with CGD, over one-third with invasive pulmonary fungal infections were asymptomatic [50].

The most common sites for abscesses are perianal/perirectal and the liver. Gingivitis, stomatitis, gastroenteritis, and otitis are also common [2,4-7,9].

Organisms — In general, the organisms that infect patients with CGD are catalase producing. Catalase is an enzyme that inactivates the hydrogen peroxide normally produced by some bacteria and fungi during growth. Although most microorganisms produce hydrogen peroxide, some do not. It was thought that CGD phagocytes could use the hydrogen peroxide produced by catalase-negative microbes to generate reactive oxidants, thereby bypassing the intrinsic CGD defect. However, the majority of pathogens in general are catalase positive, and only a few cause infections in CGD, suggesting that catalase production alone is insufficient for pathogenicity. Furthermore, targeted deletion of the catalase genes in Aspergillus nidulans and Staphylococcus aureus did not affect virulence in animal models of CGD, indicating that microbial catalase is not a significant virulence factor for CGD infections.

The overwhelming majority of severe infections in North America are due to five organisms (estimated incidence of severe infections in 268 patients followed at a single center over a 40-year period is shown) [45]:

●Aspergillus species (2.6 cases per 100 patient-years)

●S. aureus (1.44 per 100 patient-years)

●Burkholderia (Pseudomonas) cepacia complex (1.06 per 100 patient-years)

●Serratia marcescens (0.98 per 100 patient-years)

●Nocardia species (0.81 per 100 patient-years)

Another series of 27 patients followed at a different center in North America from 1985 to 2013 found that the most common causes of severe infections, in order of frequency, were S. aureus, Serratia, Klebsiella, Aspergillus, and Burkholderia [49].

Outside of North America, Salmonella and Bacillus Calmette-Guérin (BCG) are frequent infections and should suggest the diagnosis. Other organisms isolated less frequently include Streptococcus species, Neisseria meningitidis, Acinetobacter junii, Candida species, Klebsiella pneumoniae and Klebsiella oxytoca, Mycobacterium tuberculosis, nontuberculous mycobacteria, Proteus species, Actinomyces [51], methylotrophic bacteria [52], and Leishmania species [4,6,7].

Bacterial infections — The frequency of bacterial infections in CGD has decreased since trimethoprim-sulfamethoxazole prophylaxis became routine in the 1980s. Most lung, skin, and bone infections were staphylococcal in the preprophylaxis era. On prophylaxis, staphylococcal infections are essentially confined to the liver, lymph nodes, and skin [2]. Severe, resistant facial acne and painful inflammation of the nares are common infectious skin manifestations of S. aureus infection. Other bacteria and fungi are now the more common causes of lung and bone infections in patients with CGD. (See "Chronic granulomatous disease: Treatment and prognosis", section on 'Antibacterial prophylaxis'.)

B. cepacia complex, which is a common cause of pneumonia with primarily endobronchial disease in patients with cystic fibrosis (CF), can cause pneumonia with nodular infiltrates in patients with CGD, as well as hemophagocytic lymphohistiocytosis (HLH) [53-56]. Patients with CGD are prone to recurrent pulmonary infection with different strains of Burkholderia, unlike patients with CF, who tend to have chronic infection with the same strain [54].

Infants often present with Serratia marcescens bone and soft tissue infections [48]. S. marcescens infections still occur in older children and adults with CGD, but the pattern of presentation is different [57]. Osteomyelitis is rare, but disseminated abscesses and skin infections with large, poorly healing ulcers are common.

Mycobacterial infections accounted for almost 6 percent of pneumonias in American CGD surveys in 2000 and 2007 [2,58]. A high incidence of tuberculosis (TB) was observed in CGD patients living in areas endemic for TB [59,60]. Draining skin lesions at sites of BCG vaccination are seen in CGD patients, although these infections do not usually disseminate, as occurs in infants with severe combined immunodeficiency (SCID). However, dissemination of BCG may be strain dependent since numerous cases of disseminated BCG in CGD have been reported in particular countries where different strains are found [61].

Granulibacter bethesdensis is an environmental organism that can cause fever, weight loss, and necrotizing pyogranulomatous lymphadenitis [62,63]. Fatal bacteremia and meningitis have been also reported [64,65].

Bacteremia is uncommon, but, when it occurs, it is usually due to the following organisms:

●B. cepacia complex [66-68]

●S. marcescens, which is also a common cause of bacterial osteomyelitis [48]

●Chromobacterium violaceum, a gram-negative rod found in brackish water, especially in the Southeastern United States [69,70]

Infection with catalase-negative organisms is uncommon, but severe chronic recurrent actinomycosis has been reported [51]. All patients in one series presented with a prolonged history of fever and clinical signs of infection without an obvious focus. Sites of infection were cervicofacial, hepatic, and/or pulmonary [71].

Fungal infections — Fungal infections remain the leading causes of mortality in CGD [2], even though the rate of fungal infections is lower than bacterial infections. The frequency of, and mortality from, fungal infections has been markedly reduced since the advent of itraconazole prophylaxis and the use of voriconazole and posaconazole for treatment of filamentous fungal infections (eg, Aspergillus). However, fungal infections continue to occur, even in those on azole antifungal prophylaxis [50]. (See "Chronic granulomatous disease: Treatment and prognosis", section on 'Antifungal prophylaxis'.)

The fungal organisms that break through azole prophylaxis are usually resistant and require more aggressive diagnosis and therapy. A major recognition has been that the organisms frequently determined morphologically to be Aspergillus fumigatus are, in fact, non-fumigatus Aspergillus species, which is best determined by molecular speciation. Many of these organisms are more virulent in CGD than A. fumigatus, require combination antifungal therapy, and may require surgical management [72,73]. Similarly, morphologic diagnosis can be misleading for organisms often thought to be Paecilomyces variotii that are in fact the more treatment-refractory Geosmithia argillacea [74,75].

Fungal infections typically begin in the lung after inhalation of spores or hyphae. Fungal spores are common in the air in general, but specific exposures are problematic for patients with CGD, such as gardening, yard work, lawn mowing, leaf raking, and mulching. Fungal pneumonia may spread locally to ribs and spine or metastatically to brain. Aspergillus nidulans, an organism that infects patients with CGD almost exclusively, causes a significantly higher rate of osteomyelitis and mortality than other fungi [47,76]. Penicillium piceum is a relatively nonpathogenic fungus that can produce lung nodules and osteomyelitis in CGD [77]. In contrast, zygomycosis is rare in patients with CGD and is typically associated with iatrogenic immune suppression [78]. Histoplasmosis and coccidioidomycosis have not been reported in patients with CGD.

Inflammatory and other manifestations — Patients with CGD are also prone to granulomata of various organs, growth retardation, chronic pulmonary disease, and autoimmune disorders including inflammatory bowel disease (IBD). In contrast to many other immunodeficiencies, CGD is probably not associated with an increased incidence of neoplasia, although several cancers have been identified in patients with CGD [79]. The microbiome is an essential regulator of inborn errors of immunity, with accumulating evidence of connections between altered gut microbiota and clinical symptoms [80-82]. The microbiome is abnormal in CGD-associated colitis, and altered functional characteristics probably contribute to pathogenesis [83].

Granulomata — Patients with CGD are prone to the formation of granulomata. These can affect any hollow viscus but are especially problematic in the gastrointestinal and genitourinary tracts [84]. Other tissues and organs, such as the retina, liver, lungs, and bone, may also be affected by granulomata [85]. The reasons for granuloma formation in CGD are unknown, but CGD cells fail to degrade chemotactic and inflammatory signals normally and fail to degrade apoptotic cells normally, which may lead to persistent and exuberant inflammation.

Gastrointestinal — Gastrointestinal manifestations of CGD include abdominal pain, diarrhea, colitis, proctitis, strictures, fistulae, and obstruction. In a series of 140 CGD patients, 43 percent of X-linked and 11 percent of autosomal recessive CGD patients had gastrointestinal manifestations [1]. All patients with confirmed IBD complained of abdominal pain. Diarrhea was reported in 39 percent and nausea and vomiting in 24 percent. Thirty-five percent had gastrointestinal obstruction (gastric, esophageal, duodenal, and other). Bowel strictures and fistulae are present in a significant number of patients. Upper gastrointestinal tract inflammatory disease is common, although typically not as severe as colonic disease [86].

Sixty-five percent of the patients in one series with gastrointestinal involvement had either granulomatous or ulcerative colonic lesions [1]. Crohn disease and ulcerative colitis were diagnosed in only 20 percent of those with inflammatory bowel lesions. The CGD genotype appears to accentuate the standard genetic risks associated with IBD [87]. CGD should be on the differential in early-onset IBD [88]. The granulomata in CGD IBD were characterized by sharply defined histiocyte aggregates with surrounding lymphocytic inflammation, unlike the poorly formed granulomata seen in Crohn disease. However, when staining for the macrophage marker CD68 was done, CGD bowel disease had much lower levels of staining than either normal patients or patients with Crohn disease who did not have CGD [89]. This appears to be related to CD68 expression since other markers of macrophage number are similar between Crohn disease and CGD. While IBD is common in CGD, the rate of CGD in general IBD is not clear; it may account for approximately 1 percent of cases. Genome-wide association studies (GWAS) in patients with early-onset IBD have repeatedly identified the genes involved in the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase [90].

It is important to keep CGD granulomatous colitis in mind since patients with CGD have a much worse (and sometimes fatal) outcome with tumor necrosis factor (TNF) alpha inhibition (eg, infliximab) than do typical patients with Crohn disease [91,92]. (See "Clinical presentation and diagnosis of inflammatory bowel disease in children" and "Overview of the management of Crohn disease in children and adolescents" and "Treatment of Crohn disease in adults: Dosing and monitoring of tumor necrosis factor-alpha inhibitors" and "Chronic granulomatous disease: Treatment and prognosis", section on 'Therapy for inflammatory manifestations'.)

Hepatic — Liver abnormalities are frequently identified. In a CGD cohort of 194 patients, liver enzymes were elevated in 73 percent, with persistent elevations of alkaline phosphatase seen in 25 percent. Drug-induced hepatitis was reported in 15 percent. In patients with abnormal liver enzymes who underwent liver biopsy, histology revealed granulomata in 75 percent and lobular hepatitis in 90 percent. Eighty percent of patients had a portal venopathy that was often associated with splenomegaly. Liver abscesses and hepatomegaly were each seen in one-third of cases. Portal hypertension was an important risk factor for mortality and was strongly suggested by a decreasing platelet count over time [93,94].

Genitourinary — Urologic disorders are fairly common. In a series of 60 CGD patients, approximately 40 percent of patients had urologic manifestations, including ureteral and urethral strictures, urinary tract infections, altered kidney function, and bladder granulomata [95]. Colitis associated with CGD can also result in fistula formation causing urogenital tract dysfunction [96]. All patients with urologic strictures had defects of the membrane component of the NADPH oxidase (gp91phox or p22phox).

Ophthalmic — Chorioretinal lesions are described in up to one-quarter of patients with X-linked CGD [97] and are also detected in some X-linked female carriers. These lesions are mostly asymptomatic retinal scars associated with pigment clumping. Some of these lesions contain bacterial DNA (detected by polymerase chain reaction [PCR]) [98]. The clinical meaning of this finding is unclear, but it may reflect remote seeding. However, these lesions do not progress despite aggressive immunosuppression in some cases, suggesting that they are not sites of active infection. Keratitis has also been reported [4]. (See 'X-linked carriers' below.)

Pulmonary — Chronic respiratory disease, presumably due to recurrent pulmonary infections, is common, particularly in adults [4,50,84]. Findings on chest computed tomography (CT) include bronchiectasis, obliterative bronchiolitis, and chronic fibrosis [4,84]. (See "Pulmonary complications of primary immunodeficiencies", section on 'Chronic granulomatous disease'.)

A clinical entity specific to CGD is mulch pneumonitis, so-called because patients with CGD can develop a characteristic syndrome of dyspnea, hypoxia, and fever leading to respiratory failure and death within 1 to 10 days after inhalation of large burdens of fungal spores and hyphae, such as those found in mulch, hay, peat moss, or dirt [99]. This syndrome is important to recognize since it is best treated with simultaneous administration of glucocorticoids and antifungals.

Potentially noninfectious respiratory events (defined as a radiologic pulmonary opacity that often has an inflammatory pattern and is not proven to be caused by an infection) are common in adults with CGD, occurring in 28 percent of adults in one series [50]. Approximately two-thirds of these patients presented with respiratory symptoms, and most received treatment with immunomodulatory therapies, such as systemic glucocorticoids with or after treatment for infections.

Oral — Recurrent aphthous ulceration is common in CGD and especially common in X-linked carriers. Other oral manifestations may include periodontitis, gingivitis, and gingival hypertrophy [4,100,101].

Skin — Noninfectious skin manifestations of CGD include photosensitivity, discoid lupus, granulomatous lesions, and vasculitis [4].

Autoimmune — Autoimmune disorders are more common in CGD, affecting up to 5 percent of patients [2]. Both discoid and systemic lupus erythematosus (SLE) have been described and occur with at least the same frequency in X-linked CGD female carriers as in patients [102,103]. Immune thrombocytopenia (ITP) and juvenile idiopathic arthritis (JIA) are also more frequent in CGD than in the general population [2]. Other reported autoimmune diseases in patients with CGD include fibrotic pulmonary disease, immunoglobulin A (IgA) nephropathy, antiphospholipid syndrome, and recurrent pericardial effusion [104].

Growth retardation — Patients with CGD commonly experience growth retardation. Failure to thrive is a frequent presenting symptom in young children. In one series of 94 patients, approximately 75 percent were below the population mean for height and weight at the time of diagnosis [4]. Thirty-five percent required nasogastric and/or parenteral nutritional supplementation. In another small series of 23 patients, approximately 20 percent were below the 10^th percentile for height and weight [5]. Growth often improves in late adolescence [105], and many patients with CGD attain their expected growth potential by adulthood. Hematopoietic cell transplantation appears to correct most cases of growth retardation regardless of the cause [106].

McLeod syndrome — The Kell metallo-endopeptidase (KEL) gene locus on chromosome 7q33 encodes the Kell blood group proteins, of which there are more than 25 antigens. The Kell blood group system is formed by two disulfide-linked proteins, Kell and Kx, which is encoded by X-linked Kx blood group (XK), telomeric to CYBB on chromosome Xp21. Patients with deletions in the X chromosome may have deletions in portions of both CYBB and XK (contiguous gene disorder) and thereby present with X-linked CGD and McLeod syndrome. McLeod syndrome causes acanthocytosis and low or absent expression of the erythrocyte blood group Kell antigens, Kell(-). This may result in anemia, elevated creatine phosphokinase, and late-onset peripheral and central nervous system manifestations. (See "Burr cells, acanthocytes, and target cells: Disorders of red blood cell membrane", section on 'Blood group abnormalities' and "Neuroacanthocytosis", section on 'Mcleod syndrome' and "Red blood cell antigens and antibodies", section on 'Kell blood group system'.)

Special care has to be taken when transfusing patients with X-linked CGD/McLeod syndrome to avoid Kell(+) transfusions into these Kell(-) patients [107,108]. All X-linked CGD patients should be tested for Kell antigens. Those who test negative should have this noted on their medical record and wear medical identification jewelry stating that they must be given Kell(-) blood if they require a transfusion.

X-linked carriers — The X-linked carrier state for gp91phox is neither silent nor static. In affected females, lyonization (the inactivation of one or the other X chromosome in every cell) leads to two populations of phagocytes: one with normal respiratory burst function (positive dihydrorhodamine [DHR] 123 test) and the other with impaired respiratory burst activity [109]. Therefore, X-linked CGD carriers display a characteristic mosaic pattern on respiratory burst testing of peripheral blood cells as seen microscopically (nitroblue tetrazolium [NBT] test) or by flow cytometry (DHR test). (See 'Neutrophil function tests' below.)

As few as 20 percent of cells having normal respiratory burst activity is sufficient to prevent most severe bacterial and fungal infections. Thus, most female carriers of X-linked gp91phox CGD variants are not compromised in their ability to handle infections. However, carriers with less than 20 percent of normal oxidase activity due to skewed X-chromosome lyonization may present with the phenotype of mild to severe CGD [110-113]. In a large series of X-linked carriers, those with <20 percent DHR+ cells had serious infectious complications, while all carriers, regardless of percent DHR+ cells, had increased rates of inflammatory and autoimmune complications [114]. In addition, progressive skewing of X-chromosome inactivation with age in previously healthy carriers of gp91phox null variants can lead to late-onset manifestations of CGD [115]. Females may have other manifestations of heterozygous carriage of X-linked CGD variants, including discoid lupus erythematosus, aphthous ulcers, chorioretinal lesions, and photosensitivity [116,117], which are not dependent upon the degree of lyonization but appear to correlate with lyonization per se [118].

LABORATORY FINDINGS — Certain abnormalities in routine laboratory tests are associated with the disease, although these are not required for diagnosis:

●Hypergammaglobulinemia, possibly due to chronic inflammation

●Low numbers of circulating memory B cells [119]

●CD4 T cell lymphocytopenia, which may be marked, but does not correlate with infection risk nor predispose to T cell-dependent pathogens [120]

●Anemia of chronic disease

●Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), usually in the presence of infection

●Hypoalbuminemia, found in 70 percent of patients with gastrointestinal involvement and 25 percent without gastrointestinal manifestations [1]

DIAGNOSIS — Patients suspected of having CGD should initially undergo neutrophil-function testing. Positive findings should be confirmed by genotyping. It is important to appreciate that the p47phox pathogenic variant is due to a pseudogene conversion and so may not be detectable by standard sequencing. In these cases, an immunoblot or gene dose determination may be needed to confirm p47phox deficiency.

A history of recurrent and/or unusually severe infections, particularly abscesses and infections caused by the pathogens commonly associated with CGD, should prompt functional or genetic screening. Neonatal or early postnatal screening of potentially affected children is essential with a family history of CGD. (See 'Infections' above.)

Neutrophil function tests — Diagnostic tests for CGD rely on various measures of neutrophil superoxide production. These include direct measurement of superoxide production, cytochrome c reduction assay, chemiluminescence, nitroblue tetrazolium (NBT) reduction test, and dihydrorhodamine (DHR) 123 oxidation test.

Most prefer the DHR test because of its objectivity, relative ease of use, ability to distinguish between X-linked and autosomal forms of CGD, and the ability to detect gp91phox carriers [121,122]. Other tests can also provide reliable diagnosis of CGD but either cannot distinguish carrier status or require significant operator experience.

Dihydrorhodamine 123 test — In this test, the nonfluorescent rhodamine derivative, DHR, is taken up by phagocytes and oxidized to a green fluorescent compound by products of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (figure 2). The sensitivity and quantitative nature of this assay make it possible to differentiate oxidase-positive from oxidase-negative phagocyte subpopulations in CGD carriers and identify deficiencies in gp91phox and p47phox. DHR testing can also be quantitated to allow for allocation of cellular response into more and less impaired subgroups. The degree of residual superoxide production as measured by DHR testing provides important prognostic information that dovetails with genetic information [33,123]. (See 'Genetic testing' below.)

Other conditions that affect the neutrophil respiratory burst, giving abnormal DHR test results but normal measures of extracellular superoxide production (eg, cytochrome c reduction or NBT tests), include myeloperoxidase deficiency and the syndrome of synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) [124,125]. The DHR test can also be used to determine chimerism status following hematopoietic cell transplantation [126,127]. Several reference laboratories in the United States and around the world offer these assays.

Nitroblue tetrazolium test — The oldest laboratory test for CGD is the NBT test. This provides a simple and rapid (but largely qualitative) determination of phagocyte NADPH oxidase activity. Superoxide produced by normal peripheral blood neutrophils stimulated in vitro reduces yellow NBT to dark-blue/black formazan, which forms a precipitate in the cells. Normal phagocyte oxidase activity will result in at least 95 percent positive cells in this assay. X-linked carriers can be identified with this test. Test limitations include a higher rate of false-negative results and operator subjectivity.

Genetic testing — The clinical history usually suggests autosomal recessive or X-linked disease, based on sex, consanguinity, age at presentation, and severity. A diagnosis of CGD based on abnormal neutrophil function should be followed by genetic testing. Sequencing of the patient's phagocyte oxidase (phox) genes to determine the exact molecular defect is recommended. Genetic testing is available through specialized commercial laboratories and selected tertiary referral centers. The most common p47phox defect can be difficult to identify genetically as it is caused by pseudogene conversion and may be missed in typical sequencing studies. For these cases, immunoblotting or flow cytometry can show absence of protein. An amplification of the various pseudogenes can also be performed to prove loss of the functional allele.

Genetic testing is increasingly important in the risk profiling of CGD. Pathogenic variants in the gene encoding gp91phox (CYBB) are usually either missense (replacement of the correct amino acid with an incorrect one but preserving protein synthesis) or nonsense (replacement of an amino acid with a stop codon leading to protein truncation and usually abrogating protein synthesis). Nonsense variants generally lead to more severe CGD with diminished survival. Missense variants that are in amino acids 1 to 309 are associated with residual superoxide formation, slight DHR positivity, and better survival. In contrast, variants at amino acids 310 and beyond affect critical protein functional domains and usually lead to complete loss of DHR activity, more severe CGD, and diminished survival [33]. Thus, gene sequencing can be used without further functional studies to predict relative mortality risk and counsel regarding bone marrow transplantation or gene therapy.

Prenatal diagnosis — If the precise pathogenic variant of a family member with CGD is known, then chorionic villus or amniotic fluid sampling can be performed to obtain a sample for genotyping of the fetus. Another testing option is to sample fetal blood and perform a DHR test.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of CGD mainly involves disorders associated with recurrent and/or unusually severe infections, particularly those caused by the pathogens commonly associated with the disease (see 'Infections' above). However, it is usually possible to differentiate between these diseases and CGD when the entire clinical picture is examined. The differential diagnosis may consider:

●Cystic fibrosis (CF)

●Hyperimmunoglobulin E syndrome

●Glucose-6-phosphate dehydrogenase (G6PD) deficiency

●Glutathione synthetase (GS) deficiency

●Crohn disease (in patients with inflammation limited to the rectum)

Patients with CF may develop B. cepacia complex infections. However, the infections in patients with CF are limited to the lung and typically occur in the setting of significant bronchiectasis, which is not as common in patients with CGD. (See "Cystic fibrosis: Clinical manifestations and diagnosis".)

Patients with hyperimmunoglobulin E syndrome develop staphylococcal infections and may develop Aspergillus infections in the lung. However, the Aspergillus infections occur only in the setting of preexisting lung cysts, which are not common in patients with CGD. Also, hyperimmunoglobulin E patients have characteristic facies and markedly elevated immunoglobulin E (IgE) levels, whereas CGD patients do not. (See "Autosomal dominant hyperimmunoglobulin E syndrome".)

G6PD deficiency and GS deficiency affect the neutrophil respiratory burst and increase susceptibility to bacterial infections [128-131]. G6PD deficiency is most often associated with some degree of hemolytic anemia, whereas CGD is not. Severe GS deficiency is also associated with hemolytic anemia, in addition to 5-oxoprolinuria, acidosis, and intellectual disability. These disorders are reviewed separately. (See "Myeloperoxidase deficiency and other enzymatic WBC defects causing immunodeficiency".)

A report of protein kinase C (PKC) delta deficiency suggested that it should be considered in the differential diagnosis in young patients with CGD-like clinical manifestations and abnormal dihydrorhodamine (DHR) assay results, even in the absence of clinical and biological manifestations of autoimmunity [132].

Patients with Crohn disease have inflammatory bowel symptoms similar to those in CGD colitis. However, Crohn disease is not associated with severe infections, as is CGD. While Crohn disease can involve any part of the gastrointestinal tract and may have extraintestinal manifestations, CGD colitis is more often rectal and perirectal and is not associated with extraintestinal manifestations. Histopathologically, CGD bowel biopsies have lipid-laden macrophages, which are not characteristic of Crohn disease.

In vitro, the respiratory burst may also be inhibited by diverse pathogens, including Legionella pneumophila, Toxoplasma gondii, Chlamydia, Entamoeba histolytica, and Ehrlichia risticii. Human granulocytic ehrlichiosis infection depresses the respiratory burst by downregulating gp91phox [133]. This effect is not diagnostically significant.

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: Inborn errors of immunity (previously called primary immunodeficiencies)".)

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 topic (see "Patient education: Chronic granulomatous disease (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Definition and age at diagnosis – Chronic granulomatous disease (CGD) is a genetically heterogeneous condition characterized by recurrent, life-threatening bacterial and fungal infections and granuloma formation. Most patients are diagnosed before the age of five years. (See 'Introduction' above and 'Epidemiology' above.)

●Pathogenesis – CGD is caused by defects in phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which comprises the phagocyte oxidase (phox). This enzyme complex is responsible for the phagocyte respiratory burst. (See 'Pathogenesis' above.)

●Genetic defects – Pathogenic variants in the genes for all six proteins (gp91phox, p47phox, p22phox, p67phox, p40phox, and essential for reactive oxygen species [EROS]) that make up the NADPH oxidase complex account for all of the known cases of CGD. Most pathogenic variants in North America are X linked (gp91phox deficiency). (See 'Genetic defects' above.)

●Types and sites of infections – Patients with CGD typically experience recurrent infections caused by bacterial and fungal pathogens. The overwhelming majority of infections in patients with CGD living in North America are due to five organisms: Staphylococcus aureus, Burkholderia cepacia complex, Serratia marcescens, Nocardia, and Aspergillus. The frequent sites of infection are lung, skin, lymph nodes, and liver. (See 'Infections' above.)

●Inflammatory manifestations – Patients with CGD are prone to the formation of granulomata that are especially problematic in the gastrointestinal and genitourinary tracts. Colitis is a common gastrointestinal manifestation. (See 'Inflammatory and other manifestations' above.)

●Carriers – Female carriers generally do not have an increased rate of infections, but they are more predisposed to certain inflammatory manifestations associated with CGD. However, females can develop typical CGD infections when oxidase activity drops to <20 percent of normal due to skewed X-chromosome lyonization. (See 'X-linked carriers' above.)

●Diagnosis – A neutrophil function test, dihydrorhodamine (DHR) 123, is the initial diagnostic test performed. A significantly abnormal finding should be confirmed by genotyping. (See 'Diagnosis' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges E Richard Stiehm, MD, who contributed as a Section Editor to earlier versions of this topic review.

The UpToDate editorial staff also acknowledges Sergio D Rosenzweig, MD, who contributed as an author to earlier versions of this topic review.