Interdigital scaling, maceration, erythema of the soles or palms, and itching is most consistent with which diagnosis?

• A. Contact dermatitis
• B. Tinea pedis/manuum
• C. Psoriasis
• D. Erythrasma

Answer: (B)

Interdigital scaling with maceration in moist skin folds, along with itching and possible involvement of the soles or palms, points to a fungal infection caused by dermatophytes. This pattern is classic for tinea pedis, and when the hands are involved as well, it’s tinea manuum. The moist, macerated interdigital areas are a hallmark of dermatophyte foot/hand infections and explain the itching.

Other conditions don’t fit this pattern as well. Contact dermatitis usually appears at a specific exposure site with vesicles and oozing rather than the characteristic interdigital maceration. Psoriasis tends to produce well-demarcated plaques with silvery scales on extensor surfaces or palmoplantar regions, not primarily the between-toes intertriginous pattern. Erythrasma shows reddish-brown patches in skin folds with minimal itching and a coral-red glow under Wood’s lamp, rather than classic interdigital scaling.

So the presentation is most consistent with a dermatophyte infection of the feet and possibly hands—tinea pedis/manuum.