Pityriasis alba

Overview
Pityriasis alba is a common skin condition mostly occurring in children and usually seen as dry, fine scaled, pale patches on their faces. It is self limiting and usually only requires use of moisturiser creams.

The condition is so named for the fine scaly appearance initially present (pityriasis) and the palor of the patches that develop (whilst "alba" is Latin for white, the patches in this condition are not totally depigmented).

Aetiology
There is no specific known cause for this condition, but any dermatitis inflammation of the skin may heal leaving pale skin, as may excessive use of corticosteroid creams used to treat episodes of eczema. The hypopigmentation is due to both reduced activity of melanocytes with fewer and smaller melanosomes.

The condition is most often seen in children between the ages of 3 and 16 years and is more common in males than females. It possibly occurs more frequently in those of light-skin, but is more apparent in those of darker complexion.

Up to a third of US school children may at some stage get this condition. Single point prevalence studies from India have shown variable rates from 8.4%, to 31%. Other studies have shown prevalence rates in Brazil of 9.9%, Egypt 13.49%, Romania 5.1%, Turkey 12% where higher rates were seen in those with poor socioeconomic conditions, and just 1% in school children in Hong Kong.

Symptoms and signs
The dry scaling appearance is most noticeable during the winter as a result of dry air inside people's homes. During the summer, tanning of the surrounding normal skin makes the pale patches of pityriasis alba more prominent.

Individual lesions develop through 3 stages and sometimes are itchy:
 * 1) Raised and red - although the redness is often mild and not noticed by parents
 * 2) Raised and pale
 * 3) Smooth flat pale patches

Lesions are round or oval, of 0.5-2 cm in size although may be larger if they occur on the body (up to 4cm), and usually number from 4 or 5 to over 20. The patches are dry with very fine scales. They most commonly occur on the face (cheeks), but in 20% appear also on the upper arms, neck, or shoulders.

Treatment
No treatment is required and the patches in time will settle. The redness, scale and itch if present may be managed with simple emollients and sometimes hydrocortisone, a weak steroid, is also used.

As the patches of pityriasis alba do not darken normally in sunlight, effective sun protection helps minimise the discrepancy in colouration against the surrounding normal skin. Cosmetic camouflage may be required.

Tacrolimus has been reported as speeding resolution.

In exceptionally severe cases PUVA therapy may be considered.

Prognosis
The patches of PA may last from 1 month to 10 years, but commonly on the face last a year or more.