Pityriasis versicolor, also known as tinea versicolor, is a mild, usually asymptomatic, chronic fungal infection of the stratum corneum of the skin, characterized by pityroid scales, hypopigmentation, or hyperpigmentation.
The pathogens of this disease are malassezia globosa, and its insoluble part contains lipase, which is present in a mosaic form in the cell wall or cell membrane system rich in glucose. Lipase decomposes lipids into fatty acids, providing a necessary source of nutrients for its own anabolic metabolism. When cell metabolism slows, lipase activity decreases accordingly. Therefore, the pathogen is mainly in the areas with rich sebaceous glands, such as chest, back, head, face, and neck, and is an opportunistic pathogen.
Signs and Symptoms
Skin lesions are most common in the chest, back, arms, and neck, as well as face, abdomen, buttocks, armpits, groin, scalp, and occipital area, usually aggravating in summer and autumn, reducing or subsiding in winter. Initial skin lesions are fine spots, gradually progressing into pinhead sized to pea sized, round or oval, sharply demarcated, smooth or slightly raised macules, covered with very thin, pityroid, shiny scales. New skin lesions are gray, yellow, light brown, or dark brown, and old skin lesions are pale. New and old skin lesions are concurrent, granophyric, and characteristic. When the scales are removed or the skin lesions heal, there are temporary hypopigmentation.
Figure 1 pityriasis versicolor
Figure 2 pityriasis versicolor
Skin lesions distribute along the hair follicles in some patients, resembling hair follicle papules covered with scales. A small number of patients have very few, large, patchy skin lesions, covered by thick scales, mostly deep brown or dark brown, rarely light colored. Sometimes, skin lesions are so large that can be mistakenly regarded as normal skin.
Patients generally have no subjective symptoms, and mild redness and pruritus are present in few patients. The illness develops very slow, and generally subsides in winter and relapses in summer.
Mild to moderate keratoderma and dermal mild monocyte infiltration can be seen. Short, thick, slightly curved hyphae and stacked, round or oval spores can be found in the middle or bottom of the stratum corneum, and some are budding, mostly in periodic acid Schiff (PAS) stain or Gomori Methenamine-Silver (GMS) stain.
According to the clinical features and positive fungal examinations, the disease can be diagnosed.
Topical keratolytic agents or other anti-fungal agents, such as compound resorcinol or miconazole cream and 20% - 40% sodium thiosulphate, twice a day for 2 weeks are appropriate.
Large areas of tinea versicolor should be treated with systemic ketoconazole 200mg once daily for 10 days, fluconazole 50mg once daily for 10 days, or itraconazole 200mg once daily for 5 - 7 days.
The regression of hypopigmentation needs a long time, and ultraviolet radiation can accelerate recovery.