Toxic Melanodermatitis

Some patients develop asymptomatic, pin-point, hyperpigmented macular lesions which appear on any part of the body irrespective of whether the area is exposed to sunlight or not. Some lesions may remain discrete, but most of them coalesce with each other to form large irregular areas of hyperpigmentation.

On the forearms and legs the pigmentation commonly occurs around the hair follicles. New lesions keep on appearing for a few weeks or even a few months and then these lesions tend to disappear spontaneously over the next several months or may even take a few years.

The cause of this disease is not known. It seems to represent a post-inflammatory hyperpigmentation initiated by a substance which reaches the skin via blood. Till the exact aetiopathogenesis is known, it is best to call this disease idiopathic guttate and confluent hypermelanosis.

Treatment

Since the cause of this disease is not known, its treatment is also empirical. If the new lesions continue to appear, the patient should be treated with systemic corticosteroids in a dose of 10 to 20 mg of prednisolone a day. This dose given over a period of four to six weeks has been observed to prevent the appearance of new lesions. Then the dose of corticosteroids can be gradually reduced by 5 mg every 1-2 weeks.

The hyperpigmented lesions tend to disappear spontaneously in the course of an year or so, but this period can presumably be shortened by local massage with keratolytic agents, or retinoic acid, hydroquinone and fluocinolone acetonide ointments massaged one after the other at night. Vitamin C in a dose of 2.5 gm twice a day may also be given.

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