A young adult presents with multiple hypopigmented macules on the upper back that become more obvious after sun exposure. Scrapings examined after mounting show short stubby hyphae with clusters of round spores described as spaghetti and meatballs. The hypopigmentation is explained by production of:
- A Melanocyte destructive antibodies
- B Azelaic acid by the organism ✓
- C Koebnerisation from scratching
- D Post-inflammatory hyperpigmentation
Correct answer: B. Azelaic acid by the organism
Explanation
Malassezia furfur converts tryptophan to azelaic acid, which competitively inhibits tyrosinase and suppresses melanin synthesis, producing the hypopigmented patches of pityriasis versicolor. The organism is lipid dependent, so lesions favour sebum rich areas like the trunk. Vitiligo destroys melanocytes and gives completely depigmented milk white macules, while post-inflammatory change causes hyperpigmentation. Treatment is with selenium sulfide shampoo or topical antifungals.
Reference: Fitzpatrick's Dermatology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.