Introduction
Pityriasis Versicolor_Disease Background 1Pityriasis versicolor is a common, benign, superficial fungal infection localized to the stratum corneum.
Epidemiology
Tinea versicolor occurs worldwide but is more common in summer than winter months. The condition affects males and females equally and does not show a preference for any ethnic group. Pityriasis versicolor predominates in adolescents and young adults when the sebaceous glands are most active.
Etiology
Pityriasis Versicolor_Disease Background 2Pityriasis versicolor is caused by lipophilic yeasts, Malassezia species, which is part of the normal flora of the human skin. Malassezia globosa is considered the most common species involved, although M sympodialis, Malassezia furfur and several other species may also contribute.
Pathophysiology
Transformation of Malassezia from its normal yeast form into a pathogenic, filamentous (mycelial) form is the key event that triggers tinea versicolor. This shift allows the organism to proliferate within the stratum corneum and produce the clinical features of the disease. Tinea versicolor tends to appear on the upper trunk because Malassezia requires lipids, and these areas have higher sebum production. Lower sebum levels in children and/or older adults likely explain why the condition is less common in those groups. Pigment changes arise from different mechanisms: Hypopigmented patches may result from melanocyte inhibition by azelaic acid and the skin’s failure to tan in summer, while hyperpigmented or erythematous lesions are thought to reflect a mild inflammatory response to the yeast.
Risk Factors
Factors that promote tinea versicolor infection are environmental conditions such as high temperature and high humidity, which are prominent in tropical and subtropical regions. Additional factors include occlusive clothing, oily skin, application of oils to skin, excessive sweating, immunocompromised conditions, malnutrition and hereditary predisposition, oral corticosteroid intake, and Cushing’s disease.