A black line on your nail (medically known as melanonychia) causes a streak of dark pigmentation that runs along the nail bed ...

In about two-thirds of people with nail melanoma, the main symptom is longitudinal melanonychia, a dark vertical streak or line under the nail plate. It may be thin or thick, and light brown to black.

Kelly Heather, 38, ended up needing brain surgery for a tumor — and it started as a discolored line on her fingernail Kelly Heather / SWNS (2) Kelly Heather, 38, first noticed a dark line on her ...

They show up as small dark marks under your nail plates and run in the same direction the nail grows. These reddish-brown streaks are 1-3 millimeters long and do not fade or blanch when you press ...