A 48-year-old obese woman presents with well-demarcated erythematous plaques in both inguinal folds, axillae, and the inframammary region for 3 months. The lesions are macerated and notably lack scaling. KOH preparation is negative. What is the most likely diagnosis?
- A Tinea cruris
- B Inverse (flexural) psoriasis ✓
- C Erythrasma
- D Intertriginous candidiasis
Correct answer: B. Inverse (flexural) psoriasis
Explanation
Psoriasis involving flexures loses its silvery scale because moisture macerates the scale away, leaving sharply marginated red plaques in body folds. This is inverse psoriasis. Fungal infections (tinea, candidiasis) typically show satellite pustules or an active scaly edge with a positive KOH, and erythrasma is reddish-brown with coral-red fluorescence under Wood lamp. Well-defined bilateral symmetrical fold involvement in a patient with friction and obesity points to flexural psoriasis.
Reference: Fitzpatrick's Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.