Melanonychia striata longitudinalis. A case report.

Melanonychia strata longitudinalis is a pigmented (dark brown-tan-black) band running in the long axis of the nail. This abnormal color of the nail plate is caused by a focal increase of melanin because of increased number and/or function of normal or abnormal melanocytes in the nail matrix. Pigmented streaks in nails due to melanocytic hyperplasia are said to be so exceedingly common in black persons as to be normal and the phenomenon is benign in the majority of cases. In our white patient reported here the pigmentation is due to epithelial hyperpigmentation without melanocytic hyperplasia or evidence of malignancy, hormonal abnormality, or other adventitious influence.