Are the brown streaks on the nails of people with skin of color always a cause for concern?

No. Pigmented streaks of the nail may be a normal variant in people with skin of color. The condition is called melanonychia striata, and it is characterized by longitudinal bands of pigmentation that may vary from light brown to dark black. Multiple bands may be seen within the same nail or, alternatively, several nails may be involved. The cause is unknown, but the rarity of bands in children may indicate that they are a sequela of accumulated trauma. Some studies have revealed that such bands are present in >75% of blacks older than 20 years. Another recent study found that simple racial variation was the most common cause of nail pigmentation in Hispanics as well, although malignancy was a cause in about 6% of cases. In general, solitary bands are of greater concern than are multiple lesions. Close examination of the nail fold may be helpful, assessing for diffusion of pigment into the surrounding skin; however, the absence of this sign does not rule out a more serious condition, such as nail unit melanoma. Other causes of nail pigmentation include drugs such as actinomycin, antimalarials, bleomycin, cyclophosphamide, doxorubicin, 5-fluorouracil, melphalan, methotrexate, minocycline, nitrogen mustard, and zidovudine, to name a few. Laugier-Hunziker syndrome, Addison’s disease, hemochromatosis, Peutz-Jegher syndrome, and vitamin B12 deficiency may also cause nail pigmentation.

Dominguez-Cherit J, Roldan-Marin R, Pichardo-Velazquez P, et al: Melanonychia, melanocytic hyperplasia, and nail melanoma in a Hispanic population, J Am Acad Dermatol 59:785–791, 2008.

Pappert AS, Scher RK, Cohen JL: Longitudinal pigmented nail bands, Dermatol Clin 9:703–716, 1991.