A 24-year-old woman of South Asian descent (Fitzpatrick type V) presents with a 18-month history of progressive white patches on her face, hands, and feet. She reports that her mother has Hashimoto thyroiditis and her sister has type 1 diabetes. On examination, the structure marked **A** in the diagram—symmetric chalk-white depigmented macules and patches with sharply demarcated borders—are distributed over the dorsal hands, periocular region, perioral area, elbows, and knees. The lesions are completely asymptomatic, and Wood lamp examination shows brilliant blue-white fluorescence. She has recently been diagnosed with autoimmune hypothyroidism and pernicious anemia. Which of the following best characterizes the pathophysiology underlying the appearance of the structure marked **A**?
A. Fungal infection of the stratum corneum causing loss of pigment production in the superficial dermis
B. Genetic mutation in the melanin synthesis pathway leading to congenital absence of pigment in acral and facial sites
C. Autoimmune destruction of melanocytes in the basal layer of the epidermis, often associated with polyglandular autoimmune syndrome
D. Post-inflammatory hypopigmentation following resolved dermatitis with preserved melanocyte function
Explanation
Why "Autoimmune destruction of melanocytes in the basal layer of the epidermis, often associated with polyglandular autoimmune syndrome" is right
The structure marked A—symmetric chalk-white depigmented macules and patches—represents the hallmark clinical manifestation of vitiligo, which is an acquired depigmentary disorder caused by autoimmune destruction of melanocytes. The clinical presentation in this case is pathognomonic: complete loss of pigment (not mere hypopigmentation), sharply demarcated borders, acrofacial distribution (hands, periocular, perioral), and critically, a strong family history of autoimmune disease (Hashimoto thyroiditis, type 1 diabetes, alopecia areata) combined with the patient's own diagnoses of autoimmune hypothyroidism and pernicious anemia. This constellation defines vitiligo associated with autoimmune polyglandular syndrome (APS), wherein CD8+ T cells and antibodies against melanocyte antigens (tyrosinase, gp100, PMEL17) drive progressive melanocyte loss. The Vitiligo Global Issues Consensus Conference (Ezzedine et al., 2012) classifies this presentation as generalized non-segmental vitiligo (Type B), the most common form, with the pathophysiology fundamentally rooted in melanocyte-specific autoimmunity rather than pigment synthesis defects.
Why each distractor is wrong
Fungal infection of the stratum corneum causing loss of pigment production in the superficial dermis: Fungal infections (tinea versicolor, pityriasis alba) produce hypopigmentation, not complete depigmentation; they show scaling, are often pruritic, and do not have the sharply demarcated convex borders or brilliant blue-white Wood lamp fluorescence seen here. The asymptomatic nature and complete loss of melanin rule out fungal etiology.
Genetic mutation in the melanin synthesis pathway leading to congenital absence of pigment in acral and facial sites: Congenital depigmentary disorders (piebaldism, Waardenburg syndrome) present from birth or early childhood with stable, non-progressive lesions. This patient's lesions began at age 22–23 and are actively spreading (Koebner phenomenon positive), indicating an acquired, progressive process, not a congenital genetic mutation.
Post-inflammatory hypopigmentation following resolved dermatitis with preserved melanocyte function: Post-inflammatory hypopigmentation is typically dull off-white (not brilliant chalk-white), shows gradual repigmentation over months to years as melanocytes recover, and is not associated with leukotrichia (white hairs) or the strong autoimmune polyglandular history. The Wood lamp appearance and complete loss of pigment distinguish true vitiligo from post-inflammatory changes.
High-YieldNEET PG
Vitiligo = acquired autoimmune melanocyte destruction; when symmetric, acrofacial, and associated with other autoimmune conditions (thyroiditis, pernicious anemia, alopecia areata), think polyglandular autoimmune syndrome and screen for Addison disease and type 1 diabetes.
Ezzedine K et al. Revised classification/nomenclature of vitiligo and related issues: the Vitiligo Global Issues Consensus Conference. Pigment Cell Melanoma Res 2012;25(3):E1-E13.
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