Phylloid hypermelanosis and melanocytic nevi with aggregated and disfigured melanosomes: causal relationship between phylloid pigment distribution and chromosome 13 abnormalities.

The mosaic pattern of phylloid hypomelanosis is mostly associated with chromosome 13 abnormalities. Recently, 1 case of hypermelanosis in a phylloid pattern has been described. We describe a 29-year-old Japanese male with mental retardation, phylloid hypermelanosis and histopathologically and ultrastructurally peculiar melanocytic nevi, which were associated with 3 aberrant chromosome 13 cell lines.