Cutaneous hypermelanosis and intramelanotic lipid droplets.

Intramelanocytic lipid droplets have been observed in 12 patients with different types of hypermelanosis of the skin. These include drug-induced hypermelanosis, hypermelanosis secondary to use of physical agents, hypermelanotic morphea, generalized scleroderma with diffuse hypermelanosis, a hyperkeratotic tumor in xeroderma pigmentosum, aberrant mongolian spot, and methoxsalen-ultraviolet-A-induced hypermelanosis. Lipid storage was selectively observed in melanocytes. Most of the melanocytes with lipid vacuoles showed ultrastructural signs of hyperactive melanosome synthesis and certain cytoplasmic abnormalities such as melanosomal autophagic vacuole formation and mitochondrial alterations. The importance and the origin of the lipid droplets remain unclear.