Acquired patch-type blue nevus with overlying vitiligo: a case report.

BACKGROUND: Blue nevi are a group of congenital and acquired dermal melanocytoses characterized by a blue-gray appearance on the skin. The common blue nevus and cellular blue nevus are the most common subtypes. Patch-type blue nevus is rather rare.

OBSERVATIONS: We describe a 77-year-old Chinese male with a 6 × 8-cm non-palpable blue patch overlaid by a depigmented patch on the back of the left scalp. Histological examination of the blue-gray patch showed numerous spindled and elongated bipolar dendritic melanocytes in the upper reticular dermis and an absence of epidermal melanocytes. Immunohistochemically, these dendritic melanocytes were positive for S-100 and HMB-45. A diagnosis of a patch-type blue nevus with overlying vitiligo was made after the biopsy.

CONCLUSIONS: The patient presents an unusual manifestation of patch-type blue nevi with overlying vitiligo. To the best of our knowledge, these features have not been previously described.