Question
Tinea versicolor
Answer
Tinea versicolor (pityriasis versicolor) is a common, chronic, superficial fungal infection of the skin caused by Malassezia species (notably Malassezia furfur, part of the lipophilic yeast flora normally present on healthy skin, which becomes pathogenic under certain conditions — heat, humidity, hyperhidrosis, oily skin, immunosuppression — converting from the yeast to a mycelial/hyphal form).
Clinical features: multiple, well-demarcated, scaly macules/patches, typically on the trunk, neck, and upper arms, that can appear hypopigmented, hyperpigmented, or reddish-brown (“versicolor” reflecting this variable colour) — hypopigmentation results from the organism’s production of azelaic acid, which inhibits melanocyte tyrosinase, reducing melanin production in affected skin (lesions may become more noticeable after sun exposure, as unaffected surrounding skin tans normally while lesions do not).
Laboratory diagnosis:
- Wood’s lamp examination — lesions show a characteristic pale yellow-green fluorescence under UV light, useful for a rapid bedside screen and for delineating the extent of lesions.
- Direct KOH microscopy of skin scrapings — shows the characteristic “spaghetti and meatballs” appearance, short hyphal fragments (spaghetti) admixed with clusters of round yeast cells (meatballs).
- Culture is not routinely performed for diagnosis (the organism is lipophilic and requires special lipid-supplemented media to grow, making it impractical for routine use), since direct microscopy is usually sufficient and diagnostic.
Treatment: topical antifungal agents (selenium sulfide shampoo/lotion, ketoconazole shampoo, or topical azoles) for localized disease; oral antifungals (itraconazole, fluconazole) for extensive or recurrent disease; recurrence is common, given the organism’s status as normal skin flora that merely requires the right conditions to become symptomatic again.