Histochemical and ultrastructural study of diffuse melanoderma after bone marrow transplantation.

Hyperpigmentation is a well-recognized feature of cutaneous graft-versus-host disease (GVHD), and is usually restricted to sites where lichenoid or sclerodermiform lesions have occurred. Since 1975, two of 745 patients treated by allogeneic bone marrow transplantation in our institution have developed diffuse melanoderma which differed considerably from the classic presentations. They both developed acute GVHD, then lichen planus-like chronic lesions and diffuse melanoderma. Histology of biopsies of the pigmented skin showed intense pigment deposition in the basal and suprabasal layers, and in dermal macrophages. On split-dopa, melanocyte counts were 98 and 93 per field, respectively. Electron microscopy showed melanocytes protruding into the dermis, and dark melanosomes in all epidermal layers and in macrophages. These findings were suggestive of post-inflammatory hyperpigmentation. In bone marrow recipients, de novo melanoderma is a rare event which could represent a feature of cutaneous GVHD in pigmented subjects.