Diffuse dermal melanocytosis in two patients with Sandhoff disease and mucopolysaccharidosis VI.

Dermal melanocytosis (DM) is described as the presence of ectopic melanocytes in the dermis and could be a normal cutaneous finding. However, diffuse DM or extensive Mongolian spots must be considered as an early sign of neurometabolic diseases, in particular lysosomal storage disorders. The presence of extensive DM should alert the physician to the presence of such disorders, making early diagnosis possible. We describe for the first time the presence of DM in two patients with Sandhoff disease and mucopolysaccharidosis VI.