Pigmented longitudinal bands of the nail. A clinicopathologic study.

Eighteen patients with pigmented longitudinal bands of the nail were evaluated. The following clinical data were obtained: age, gender, and race, duration of the pigmented bands, description and location of the lesion, history of any clinical changes; other nail changes; and family and past history. Nail matrix and/or nail bed biopsy were performed in all cases. The histopathologic findings of 18 patients with longitudinal melanonychia showed hyperpigmentation of the epidermis with no apparent increase in the number of melanocytes in 10 cases. One case showed melanoma in situ; another showed keratinocytic proliferation with focal atypia. Three cases showed subungual hemorrhage. The cause of solitary pigmented bands is often not readily apparent, making the clinical diagnosis challenging. Melanotic macule of the nail matrix, consisting of increased pigmentation of the epidermis with no apparent increased in the number of melanocytes, seems to be the most common cause. When the cause of longitudinal melanonychia is not clinically apparent, biopsy of the nail matrix and the nail bed should help to establish it.