Ethnic-type pigmentation
From dermoscopedia
Ethnic-type pigmentation is also often a polydactylic condition and family history helps in its diagnosis. As it predominates on the right hand in right-handed patients (and the opposite in left-handed) and occurs in darkskinned persons, it is likely that it could also correspond to some kind of repetitive trauma-induced pigmentation. Nevertheless, the dermoscopic aspect is similar, involving a grayish subtle dermoscopic pigmentation.
