Circumscribed alopecia areata incognita.

The characteristic lesion of alopecia areata is a smooth bald patch on the scalp. When there is no bald surface it is called alopecia areata incognita. To date, all cases of alopecia areata reported as so-called 'incognito' have shown a diffuse involvement of the scalp as in acute telogen effluvium. Recently, we have observed two patients who showed localised hair thinning of the scalp without bald spots. Histopathologically, the lesions were typical of alopecia areata with peribulbar lymphocytic infiltrates. The response to corticosteroid treatment and its clinical course were also compatible with alopecia areata.