10 Nail Changes That May Indicate an Underlying Health Issue

6. Dark Lines and Pigmentation - Melanoma and Ethnic Considerations

Dark lines, bands, or pigmentation changes in nails require careful evaluation as they can range from benign ethnic variations to potentially life-threatening melanoma, making accurate diagnosis crucial for appropriate treatment and prognosis. Longitudinal melanonychia, appearing as brown or black bands running from the cuticle to the nail tip, occurs normally in up to 90% of individuals with darker skin tones but should be evaluated with suspicion in fair-skinned individuals or when certain warning signs are present. Subungual melanoma, though rare, represents one of the most dangerous forms of skin cancer and can initially present as a dark band that gradually widens, develops irregular borders, or extends into the surrounding skin (Hutchinson's sign). The ABCDEF criteria for nail melanoma assessment includes Age (peak incidence 50-70 years), Band characteristics (brown-black, width >3mm, irregular borders), Change in the band over time, Digit involvement (thumb, great toe, or index finger most common), Extension into surrounding tissue, and Family history of melanoma. Other causes of nail pigmentation include drug-induced changes from medications such as antimalarials, chemotherapy agents, or antimicrobials, as well as systemic conditions like Addison's disease, HIV infection, or nutritional deficiencies. Trauma-related pigmentation typically presents as a more uniform discoloration that gradually grows out with the nail, unlike the persistent or progressive nature of melanoma. Professional dermatological evaluation, including dermoscopy and possible biopsy, is essential for any concerning pigmented nail lesion, particularly those that develop suddenly, change over time, or occur in individuals without typical ethnic predisposition to nail pigmentation.