Reticular erythematous mucinosis: light and electron microscopy, immunofluorescence and histochemical findings.

Five patients with reticular erythematous mucinosis were studied by skin biopsy and phototesting. Light microscopy showed a dermal mononuclear cell infiltrate (composed largely of lymphocytes), separation of collagen bundles and fragmentation of elastic fibres. Histochemical stains showed increased dermal mucin with a profile consistent with hyaluronic acid. In one case, the ultrastructural distribution of mucin was demonstrated using colloidal iron staining, electron microscopy and X-ray microanalysis. In two cases, virus-like tubular aggregates were identified in the cytoplasm of dermal endothelial cells and pericytes. Immunofluorescent staining for immunoglobulins, fibrin and complement was negative.