Tinea versicolor, also known as pityriasis versicolor, is a hypopigmented, hyperpigmented or erythematous macular eruption in which the macules may coalesce into large patches with an adherent fine scale. The scaling is very superficial and can be accentuated by gently scraping with a fingernail. The infection tends to be persistent and flares in high temperatures and humidity.

Differential diagnosis

Seborrheic dermatitis, contact dermatitis, tinea coporis, pityriasis alba, and vitiligo are included in the differential diagnosis. KOH examination of scale from the lesions will reveal short, curved hyphae and circular spores presenting as the characteristic "spaghetti and meatballs" appearance. Wood's light examination reveals an orange fluorescence.

Pathophysiology

Tinea versicolor is a benign overgrowth of the yeast Pityrosporum orbiculare or ovale. The organism is also called Malassezia furfur. The yeast inhibits the tyrosinase activity of melanocytes which results in decreased melanin production. The dark spots are hypothesized to be produced by the inflammation in response to the infection.

Treatment

Selenium sulfide, zinc pyrithione, or ketoconazole shampoo applied to the affected lesions are the treatment of choice. Oral ketoconzole, itraconazole or fluconazole in a single dose may be sufficient to clear up the infection. Recurrence is common in those predisposed to Pityrosporum overgrowth.