Idiopathic eruptive macular pigmentation with papillomatosis: Report of nine cases.

Nine patients, seven males and two females aged 6-14 years, presented with extensive, asymptomatic, brown-black macules and mildly elevated, pigmented lesions of a few months' duration. The sites affected were the face, trunk and proximal extremities. The skin lesions were discrete and individual lesions were less than 2 cm in size. The clinical diagnoses rendered by the referring physicians were lichen planus pigmentosus, urticaria pigmentosa, erythema dyschromicum perstans and postinflammatory hyperpigmentation. Histology in all nine cases showed papillomatosis of the dermis with prominent pigmentation of the basal layer (pigmented papillomatosis) without any significant dermal inflammation. Two cases had spores of Pityrosporum ovale in the thickened horny layer, one of which also had, in addition, bacterial colonies in the stratum corneum. The pigmentation resolved on its own over several months. This presentation is similar to the previously described idiopathic eruptive macular pigmentation with the additional histological finding of papillomatosis that is being described for the first time and may be nosologically related to acanthosis nigricans and confluent and reticulate papillomatosis.