Pityriasis (bran-like) versicolour (varying in colour) is a chronic infection characterised by multiple macular patches varying in size and degree of brown pigmentation occurring on the trunk.
Caused by infection by the commensal yeast Pityrosporum orbiculare (also known as Malessezia furfur, Pityrosporum ovale and Malassezia ovalis). Infection results from conversion of the yeast to the mycelial or hyphal form, which may be triggered by heat and humidity and immunosuppression. The yeast releases carboxylic acids, which inhibit melanin production.
Lesions are superficial hypopigmented macules appearing light brown or salmon coloured with a fine scale. They are most seen commonly on the upper trunk and proximal limbs.
Treated with topical antifungal agents for 2 weeks. Oral antifungals may be used for extensive disease. Recurrence is common, and frequent relapses may require prophylaxis with topical selenium sulfide or an oral conazole. The loss of colour in the skin may persist for several months after treatment.
The ichthyoses are disorders of keratinisation, which may or acquired characterised by a generalized be congenital scaling of the skin due to hyperkeratosis (see Table 9.2).
Topical emollients and bath additives are used to help avoid the dryness. Oral retinoids are used in the more severe forms.