Pityriasis versicolor (tinea versicolor)
Overview
Pityriasis versicolor is a superficial cutaneous yeast infection caused by Malassezia species (commonly M. furfur and M. globosa). These lipophilic yeasts are normal commensals of seborrhoeic skin but may overgrow and convert to a hyphal form in warm, humid conditions or with increased sebum production.
The result is well‑demarcated, scaly macules and patches with altered pigmentation. The condition is usually cosmetic and benign, but it recurs frequently and can be mistaken for other pigmentary disorders.
Epidemiology and risk factors
- Common worldwide, especially in adolescents and young adults, with peak incidence in hot, humid climates.
- Predisposing factors include heat and humidity, hyperhidrosis, oily skin, adolescence, immunosuppression, systemic or topical corticosteroid use, Cushing’s syndrome, and family tendency.
- The condition is not highly contagious; disease reflects overgrowth rather than simple transmission.
Pathogenesis
- Malassezia overgrowth and transition to a hyphal form occur in sebum‑rich areas (upper trunk, shoulders, proximal arms, neck).
- The organism produces metabolites that interfere with melanocyte function, leading to hypo‑ or hyperpigmented patches.
- Scale is confined to the stratum corneum.
Clinical features
- Lesions are multiple, well‑demarcated macules or patches with fine superficial scaling.