Longitudinal melanonychia (melanonychia striata) Nails Diseases

Longitudinal melanonychia presents a difficult clinical challenge because subungual melanoma must always be included in the differential diagnosis and because the cause of longitudinal melanonychia is usually not apparent. When melanocytes in the nail bed increase in number or activity, they may produce a pigmented band that "shines through" the nail as a gray, brown, or black spot. When the cause of longitudinal melanonychia is not clinically apparent, biopsy of the nail matrix and the nail bed should help to establish it. Nail biopsy is a safe and useful diagnostic procedure for many nail disorders when routine clinical and laboratory methods fail to produce a diagnosis. Nail bed and perionychial biopsies can be performed easily and with minimal scarring. They are most commonly used to diagnose tumors as well as infectious and inflammatory disorders of the nail. Great care must be taken in nail matrix biopsy to minimize the risk of permanent nail dystrophy.