2.3.3 Pityriasis Versicolor

The disease is most frequently found in young adults and commonly occurs in spring and summer seasons, particularly in humid climates.

Pityriasis versicolor is a superficial cutaneous mycosis caused by lipophilic Malassezia yeasts (primarily M. globosa) characterized by hypo- and hyperpigmented macules with pityriasiform scales, most commonly located on the trunk.

Causative lipophilic Malassezia yeasts belong to the resident flora of human skin. Predisposing factors that trigger hyphal growth stage include sweating, humid climate, and immunosuppression.

Malassezia species produce substances that block melanin synthesis, which may contribute to the development of hypopigmented macules.

The clinical features are variable and include several clinical types:

• Hyperpigmented type: disseminated, yellow-brown macules of 1-3 centimeters in diameter with pityriasiform scales and sometimes modest pruritus.

• Depigmented type (pityriasis versicolor alba): small white macules in dark-skinned or tanned individuals.

• Erythematous type: erythematous macules with infiltrate and only minimal scale.

• Atypical forms: solitary or few lesions, often in atypical sites.

The favoured site is the upper trunk, as it is rich in sebaceous and eccrine glands. The lower trunk and proximal extremities are less often affected.

KOH examination of a specimen taken from the scales shows grouped spores and pseudohyphae which has been described as “spaghetti and meatballs pattern”. Wood’s light (365 nm) examination reveals yellow-orange fluorescence of the affected areas.

Histology is generally not required, but if it is performed, hyphae and spores can be found in the stratum corneum.

The disease is usually recurrent, but sometimes it clears spontaneously. Pigmentary changes may remain for weeks or months after the treatment.

Vitiligo can be excluded clinically by the absence of scales. KOH and Wood’s light examination may help to exclude pityriasis alba, pityriasis rosea and seborrheic dermatitis. Another diagnostic consideration may be tinea corporis.

Patients should be advised about preventive measures that include wearing breathable fabrics, such as cotton, to decrease sweating, and avoidance of tight clothing as well as the use of oily skin products. Topical treatment of the entire body is usually effective. It includes the use of antifungal shampoos containing imidazoles (ketoconazole, econazole), selenium sulfide or zinc pyrithione; twice weekly for 2-4 weeks. In cases with frequent recurrences or widespread involvement systemic anti-fungals such as itraconazole (200 mg per os daily for 5-7 days) can be recommended.