Generally, topical coal tar preparations are safer in the long term and usually more effective than topical corticosteroids for treating psoriasis in children. There are drawbacks, however, and irritancy, cost and poor patient acceptance because of their odour may limit their use. Tars are usually started at a strength of 4% LPC on the body and limbs. This may be increased up to 10% LPC with the addition of salicylic acid to reduce scale, but this is not often required. Weak tars, usually no more than 2% LPC, may be used on the face and flexures. Tar treatment needs to be carefully monitored but when tolerated and used persistently is very rewarding. Topical corticosteroids may be used in conjunction with tars, particularly where the rash is itchy.
Calcipotriol combined with betamethasone dipropionate has good patient acceptance because of its lack of odour and can be more effective than topical corticosteroid monotherapy. It is usually well tolerated. It is too potent to use on the face and flexures in children but is useful on the trunk and limbs.
Topical pimecrolimus may also be useful for psoriasis affecting the eyelids but in general is too weak to be effective. Narrow band UVB phototherapy, oral retinoids, methotrexate and ciclosporin A may be used in very severe cases of childhood psoriasis, but this situation rarely arises and if it does, the patient needs to be referred to a paediatric dermatologist.
When an attack of psoriasis has been precipitated by a streptococcal infection, the infection should be treated with oral antibiotics. Eradication of streptococci will not always improve the psoriasis. In some patients, psoriasis is exacerbated by chronic or recurrent streptococcal infections, particularly of the ear, nose and throat. In these patients there may be a role for prophylactic antibiotics and some benefit from tonsillectomy.
Response to psoriasis treatment is typically slow, much more so than to atopic dermatitis treatment. This is because psoriasis is a hyperproliferative rather than an inflammatory condition. The normal turnover time of the epidermis is about six weeks, and this is usually the minimum time needed to obtain a good response from any treatment aimed at treating the rash. Unless patients are warned of this, many will give up long before their treatment has had a chance to become effective (see the Patient and Carer Handout). Once the rash has cleared, preventative treatment with tar ointments can be effective at maintaining remission, and topical corticosteroids should be restarted at the first sign of any new lesions.
Treatment of psoriasis can be complex, and if a patient’s response is particularly slow, referral to a dermatologist is recommended.
Pityriasis alba is a common mild form of dermatitis in which postinflammatory hypopigmentation is marked. Patients present with poorly defined hypopigmented scaly patches on the face (Figure 5). It is most obvious in summer, when the skin is tanned, and in dark-skinned children, and it is more common in children with atopy. Usually, symptoms are minimal.
Pityriasis alba must be differentiated from pityriasis versicolor, a fungal skin condition that, in children, typically occurs on the face (Figure 6). Vitiligo should also be considered as a differential diagnosis but is not scaly and has a very sharp border, with obvious depigmentation rather than hypopigmentation.
It is often not necessary to treat pityriasis alba, as it is more a cosmetic than symptomatic problem. Avoidance of skin irritants such as soap and shampoo and use of a soap substitute as well as an emollient twice daily are often all that is needed.