Thank you for writing.
Nail discoloration that occurs as a vertical line is also called longitudinal melanonychia. It occurs due to an overproduction of melanocytes in that area of the nail. These streaks in fingernails are sometimes caused by “nail moles” and similar to moles elsewhere in the body, may not develop into a more serious problem but still need to be monitored. Nail moles are more common in children.
Nail pigment bands or melanonychia are quite common in people who have dark skin. It is estimated that 70 percent of African Americans over the age of 20 have nail banding and almost all African Americans over the age of 50 have some type of nail pigment discoloration. Only 10-20 percent of those of Japanese decent have melanonychia and it occurs in less than two percent of Caucasians.
Melanonychia that is found to be skin melanoma (subungual melanoma) has the highest morbidity over other sites in the body so any nail discoloration should be evaluated by a dermatologist. The doctor will review symptoms based on an A through F list to rule out whether melanoma is the cause.
● A: Age. Subungual melanoma is more common in those ages 50 to 70.
● B: Brown/black band is wider than three millimeters.
● C: Change has been noted in the look of the pigment band.
● D: Digit involved. The thumb is the most common, then the great toe and last the index finger.
● E: Extension of the discoloration into the cuticle or nail fold (called Hutchinson sign).
● F: Family history of melanoma.
There are numerous other reasons why nail pigment banding occurs: trauma to the nail, medication, systemic diseases, vitamin deficiencies and other skin conditions which may also appear as banding in more than one finger. A doctor should review your entire medical history to determine what the next step is to take.