Idiopathic guttate hypomelanosis. Ultrastructural study

Abstract

Idiopathic guttate hypomelanosis (IGH) was studied histochemically (split-dopa) and ultrastructurally in 3 patients. Affected skin was compared to normal surrounding skin. Argentic stains revealed a decrease in the melanin content of affected epidermis and pigment granules were irregularly distributed. Split-dopa preparations showed a decrease in the number of dopa-positive melanocytes in hypomelanotic macules. Most melanocytes were round and lacked dendrites or had fragmented ones. Ultrastructural study confirmed the progressive loss of epidermal melanocytes in skin affected by IGH and revealed 2 types of melanocytes, healthy melanocytes with normal melanogenic activity and melanocytes containing few or no immature melanosomes but showing no cellular alterations. Depigmentation in IGH seems to occur in 2 stages, loss of melanogenic activity in certain melanocytes and elimination of inactive melanocytes. The basic defect in IGH melanocytes may reflect the aging process.