Pityriasis alba

 

Definition

 

This is a pattern of dermatitis in which hypopigmentation is the most conspicuous feature. Some erythema and scaling usually precede the development of hypopigmentation but these are often relatively mild.

 

Epidemiology

 

Age

 

Pityriasis alba occurs predominantly in children between the ages of 3 and 16 years.

 

Sex

 

The sexes are equally susceptible.

 

Associated diseases

 

Pityriasis alba is often a manifestation of atopic eczema but it is not confined to atopic individuals.

 

 

Clinical features

 

The lesions consist of round, oval or irregular hypo pigmented ill-defined macules and patches. They are often slightly erythematous and have fine scaling. Initially, the erythema may be conspicuous and there may even be minimal serous crusting. Later, the erythema subsides completely and, at the stage at which the lesions are commonly seen by a physician, they show only persistent fine dry, powdery scaling and hypopigmentation. It is this that usually induces the patient to seek advice. The hypopigmentation is most conspicuous in pigmented skin, and in lighter skins it becomes more apparent during the summer months when the surrounding skin is tanned. This dermatosis is generally asymptomatic, but some patients complain of itching and burning

There are usually several patches ranging from 0.5 to 2 cm in diameter, but they may be larger, especially on the trunk. In children the lesions are often confined to the face, and are most common on the cheeks and around the mouth and chin. In 20% of affected children the neck, arms and shoulders are involved as well as the face. Less commonly the face is spared and there are scattered lesions on the trunk and limbs.

Although the patches of hypomelanosis often remain stationary and unchanged for several years, they usually (but not always) clear spontaneously after puberty.

 

Differential diagnosis

 

The age incidence, fine scaling and distribution of the lesions usually suggest the diagnosis. Naevus depigmentosus most commonly presents at birth or before 3 years of age and most often causes single, well‐marginated lesions on the trunk. However, this condition may be difficult to distinguish from pityriasis alba when it occurs on the face and in cases of later onset. Nummular dermatitis in an atopic child is intensely pruritic, and the lesions are larger and more edematous. In older children and adults, early trunk lesions may be mistaken for psoriasis but the distribution and the relatively mild scaling should exclude this diagnosis.

 

 

Disease course and prognosis

 

Recurrent crops of new lesions may develop at intervals. The average duration of the common facial form in childhood is a year or more.

 

Treatment

 

Response to treatment is often disappointing, mainly because the hypopigmentation takes a long time to recover. The scaling may be reduced by a bland emollient cream. Mild topical corticosteroid such as hydrocortisone is helpful if inflammation persists. Topical tacrolimus and pimecrolimus are effective in facial atopic eczema and seem likely to prove helpful in pityriasis alba.

 

Therapeutic ladder

First line

·        Emollient

Second line

·        Mild topical corticosteroids

Third line

·        Topical tacrolimus or pimecrolimus