Pityriasis Health Dictionary

A skin disorder typi?ed by a bran-like desquamation (?aking). There are several varieties including P. alba, rosea, versicolor (fungal caused) and rubra (exfoliative dermatitis).

Pityriasis alba is a mild form of chronic eczema (see DERMATITIS) occurring mainly in children on the face and in young adults on the upper arms. It is characterised by round or oval ?aky patches which are paler than the surrounding skin due to partial loss of MELANIN pigment. The appearance is more dramatic in dark-skinned or suntanned subjects. Moisturising cream often su?ces, but 1 per cent HYDROCORTISONE cream is more e?ective.

Pityriasis rosea is a common self-limiting eruption seen mainly in young adults. It usually begins as a solitary red ?aky patch (often misdiagnosed as ringworm). Within a week this ‘herald patch’ is followed by a profuse symmetrical eruption of smaller rose-pink, ?aky, oval lesions on the trunk and neck but largely sparing the limbs and face. Itching is variable. The eruption usually peaks within 3 weeks and fades away leaving collarettes of scale, disappearing within 6–7 weeks. It rarely recurs and a viral cause is suspected but not proved. It is not contagious and there is no speci?c treatment, but crotamiton cream (Eurax) may relieve discomfort.

n. (originally) any of a group of skin diseases typified by the development of fine branlike scales. The term is now used only with a modifying adjective. Pityriasis alba is a common condition in children in which pale scaly patches occur on the face; it is related to atopic *eczema. Pityriasis rosea is a common skin rash, believed to be viral in origin, typically starting with a single patch (a herald patch) on the trunk and followed by an eruption of oval pink scaly *macules. The spots are often aligned along the ribs. The rash usually clears completely in about eight weeks. Pityriasis versicolor is a common chronic infection of the skin caused by the yeast Malassezia furfur, which produces a persistent pale or brown scaly rash on the trunk. Treatment with *selenium sulphide shampoo or with oral itraconazole readily kills the organism but the skin may take months to regain its normal colour. See also dandruff.