Melanonychia is a blackening on the nail plate by melanin pigmentation. It can often present as a darkened band under or within the nail plate. Often it runs vertically, and when it does, it's referred to as a longitudinal melanonychia or melanonychia striata.
July 1, 2006
These black bands aren’t worn for power. The dark bands on nails, melanonychia, are often harmless, but they can also be signs of cancer.
December 1, 1995
Although the cause of most nail pigment changes is benign (such as stains), more serious problems such as cancer must be considered.