Which conditions comprise the differential diagnosis for pityriasis alba?

• A. Eczema and psoriasis
• B. Vitiligo and tinea versicolor
• C. Melanoma and basal cell carcinoma
• D. Herpes zoster and impetigo

Answer: (B)

When you see pale, slightly scaly patches on a child’s face, the most relevant differential to consider is other causes of hypopigmented patches, especially vitiligo and tinea versicolor. Vitiligo presents as depigmented, sharply defined patches with no scale, often on the face or hands, reflecting loss of melanocytes. Tinea versicolor causes hypopigmented (or sometimes hyperpigmented) patches with fine scale, commonly on the trunk but may appear on the face in darker-skinned individuals, due to Malassezia infection. Pityriasis alba itself tends to have ill-defined patches with mild scaling and is common in children.

Other choices don’t fit as well because eczema and psoriasis produce inflammatory plaques with noticeable erythema and scaling rather than smooth, pale patches; melanoma and basal cell carcinoma are neoplasms with distinct pigmented or altered lesions more typical in adults; herpes zoster and impetigo present with vesicles or crusted erosions, not the subtle hypopigmented patches seen with pityriasis alba.