What is linear melanonychia?

A linear, pigmented streak of the nail (Fig. 45-3). Among the many potential causes, subungual melanoma is the most serious. A biopsy of the nail matrix is required if melanonychia develops rapidly, if it involves only a single digit, or if other causes of the abnormal pigmentation cannot be determined. This is a more common presentation of melanoma in blacks than in whites.

Note that longitudinal pigmented nail bands are commonly seen in darkly pigmented patients but are less common in light-skinned patients. If a pigmented nail band involves only one nail, occurs in a middle-aged or elderly white patient, shows progressive widening or darkening, or has an extension of pigment onto the surrounding nail fold, a biopsy is indicated to rule out melanoma.