Black pigmentation of the nails.
Darkening of the fingernails or toenails; may be seen as a black band within the nail plate, extending from the base to the free edge.
A fingernail or toenail displaying a black or dark hue is often caused by an accumulation of the pigment melanin. This often appears as a vertical stripe down the nail.
Melanonychia is commonly found in some Black and Asian individuals. In Caucasians, it could result from a naevus (a colored spot) under the nail, melanoma, a response to medication, or an HIV infection.