The biker-glove pattern of congenital melanocytic nevi.

Congenital melanocytic nevi (CMN) are common birthmarks with 20% occurring on the limbs. We describe 4 patients with acral CMN with a "biker-glove" distribution with sparing of the distal digits, as has previously been described in acral infantile hemangiomas (IH). The existence of the biker-glove pattern suggests that CMN arise from early mutations in melanocyte precursors and supports the recently described Kinsler-Larue hypothesis of mesenchymal distribution of melanocyte migration occurring in a circular field from a central point. Developmental errors in mesenchymal precursors with similar migration patterns may explain this shared pattern among CMN and IH.