Pityriasis versicolor

1 -  BACKGROUND

Pityriasis versicolor is a yeast infection of the superficial layers of the skin that is common, benign, and can occur in any site. It can affect people of all ages and both sexes, but more frequently affects adolescents and young adults. It is uncommon in children and the elderly. There is a higher incidence of pityriasis versicolor in tropical and subtropical regions. It occurs most frequently in the summer and the autumn.

Pityriasis versicolor develops when the stratum corneum of the skin becomes colonised by a lipophilic spore of the Malassezia genus. The species Malassezia furfur is known to cause pityriasis versicolor lesions. Recently, the taxonomy of the Malassezia genus has been broadened with ten species being isolated based on their molecular biology, as well as on morphological and physiological data. Malassezia globosa is thought to be main agent involved in pityriasis versicolor, while Malassezia sympodialis is thought to be the main species present in the skin flora of healthy individuals.

The lesions are unsightly hypopigmented or hyperpigmented patches that can affect any part of the skin surface except the palms of the hands and soles of the feet. Contagion between humans and indirect transmission are very uncommon and a subject for debate. The infection is caused principally by commensal microflora present on the skin. The transition from a benign to a pathogenic state often involves a change from yeast spores into mycelia or pseudomycelia. There are a number of conditions that may be favourable for proliferation of these yeasts:

– Physiology: pale or greasy skin, seborrhoeic areas of skin, hyperhidrosis and perspiration, malnutrition;

– Climate: hot weather, humidity and frequent exposure to the sun; it is for these reasons that pityriasis versicolor most commonly presents in the summer months and in patients in coastal locations. Indeed, it is the most widespread example of the “summer mycoses” that affect people in Mediterranean countries;

– Clothing: wearing tight clothing made from synthetic materials;

– Iatrogenic factors: use of corticosteroid therapy, oral contraceptives, immunosuppressant drugs, oily cosmetics, body oils, hydrating creams, oil-based sunscreens;

– Individual factors: hypercorticism (Cushing’s syndrome), pregnancy, cellular immune deficiency. However, pityriasis versicolor does not seem to be especially prevalent among patients with human immunodeficiency virus.