Chronic mucocutaneous candidiasis

Chronic mucocutaneous candidiasis (CMC) refers to a heterogeneous group of primary immunodeficiency syndromes marked by chronic or recurrent infections of the skin, nails, and mucosal surfaces (oral, esophageal, vaginal) by Candida species, most commonly Candida albicans, without progression to invasive or disseminated candidiasis. The underlying defect is impaired T-helper 17 (Th17) cell function or IL-17/IL-22 signaling, which is critical for mucosal antifungal immunity. Causes include mutations in STAT1 (gain-of-function, most common cause), STAT3, IL-17F, IL-17RA, CARD9, and AIRE (autoimmune regulator gene). AIRE mutations cause APECED (autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy), also called APS-1, characterized by the triad of chronic mucocutaneous candidiasis, hypoparathyroidism, and adrenal insufficiency (Addison disease), often with additional autoimmune endocrinopathies (e.g., hypothyroidism, type 1 diabetes) due to failure of central T-cell tolerance and autoantibody production against IL-17 and IL-22.

Clinically, patients present with recurrent oral thrush, esophagitis, chronic paronychia, nail dystrophy, and cutaneous candidal plaques that are often refractory to standard antifungal therapy and recur after treatment discontinuation. Unlike patients with neutrophil or complement defects, these patients do not develop invasive fungal disease because neutrophil and phagocytic function remain intact; the defect is specific to Th17-mediated mucosal defense.

Diagnosis involves clinical recognition of chronic/recurrent candidiasis, exclusion of HIV and other causes of immunodeficiency, autoantibody testing (anti-IL-17, anti-IL-22 in APECED), and genetic testing for STAT1, STAT3, AIRE, or other implicated genes.

Management includes long-term antifungal therapy (fluconazole, itraconazole), monitoring for and treating associated autoimmune endocrinopathies (in APECED), and in severe genetic forms, consideration of targeted therapies (e.g., JAK inhibitors in STAT1 gain-of-function mutations) or hematopoietic stem cell transplantation in select cases.

High-yield board associations: APECED = AIRE mutation, autoimmune polyendocrinopathy + candidiasis + ectodermal dystrophy (dental enamel hypoplasia, alopecia); Job syndrome (hyper-IgE syndrome, STAT3 mutation) can have mucocutaneous candidiasis but also features eczema, recurrent staph infections, coarse facies, and elevated IgE; distinguish from chronic granulomatous disease and SCID, which cause invasive fungal infections rather than isolated mucocutaneous disease.