Scleroderma: ultrastructural study of the melanin pigmentary disturbances of the skin.

Abstract

Studies of both hypermelanosis and hypomelanosis in six patients with generalized scleroderma and in two patients with localized scleroderma were performed. Examination of epidermal split dopa preparations showed an absence of dopa positive melanocytes in depigmented skin, a reduction in hypopigmented skin in which the cells were elongated, bipolar or comma-shaped, and a normal population in hyperpigmented skin, in which the melanocytes were larger, with prominent dendrites, and exhibited intense enzyme reactivity. Ultrastructural studies confirmed the disappearance of melanocytes in depigmented skin. In hypopigmented skin, the melanocytes contained few melanosomes and showed evidence of cytoplasmic degeneration (lipid vacuoles and autophagocytosis of melanosomes). In hyperpigmenred skin synthesis of melanosomes and their transfer to neighbouring keratinocytes was increased. Melanosome autophagocytosis was also observed in these specimens. No significant differences in melanosome size was found between hyperpigmented, hypopigmented or healthy skin. Hypermelanosis associated with scleroderma is due to increased activity of epidermal melanocytes and hypomelanosis is attributable to the disappearance of melanocytes.