Atypical linear nail pigmentation is melanoma clue

National report - While many of the factors of nail disorders are the same between Caucasians and people of color, there are a few signs to keep a look out for, such as the presence of nail pigmentation, according to Richard K. Scher, M.D., professor of dermatology and head of nail section at Columbia University Presbyterian Medical Center, New York.

"In terms of skin pigmentation, the major differential between people of color and Caucasians is the presence of nail pigmentation, most commonly linear nail pigmentation," he says.

"Linear nail pigmentation (or dark brown-black pigmented longitudinal bands of the nail) in people of color is considered to be a normal finding, whereas it is considered to be abnormal in Caucasians. In some cases in Caucasians, it is a sign of melanoma. Therefore, in most Caucasians, we recommend that these linear pigmented bands be biopsied," Dr. Scher explains.

However, in people of color linear pigmented bands may be not be normal if they are atypical (i.e., if one band in one nail is very different than others in other nails).

"That is considered suspicious and needs to be biopsied and determined whether or not it may be a melanoma," he says.

Rates of occurrence

Dr. Scher, who is a past president of the American Academy of Dermatology, notes that, although exact figures are not known, it is estimated that linear pigmented bands occur in about 1 percent of Caucasians, in about approximately 15 percent of Asians and as high as 50 percent or more in blacks.

He points out that the prevalence of the linear pigmented bands also varies according to the depth of skin pigmentation.

For example, for a light-skinned black patient, the prevalence of linear pigmented bands would be closer to Caucasians. On the other hand, for a dark-skinned black patient or person of Middle Eastern descent, the likelihood of having many pigmented bands on many nails is much higher.

(Dark pigmentation of the nail can also arise from other causes, including an association with certain drugs, fungal infection or trauma.)

Similarities

"Other than pigmented changes in the nails, other factors that affect the nail are relatively similar between Caucasians and people of color," Dr. Scher notes.

For example, there is no major difference in the prevalence of nail fungus or allergy to nail cosmetics between the two groups. Although psoriasis in general (not specific to nails) is thought to be less common for people of color, there is no significant difference in nail psoriasis in either group.

Dr. Scher notes that dermatologists should stay on the look out for atypical linear pigmentary bands in patients and perform a biopsy for melanoma with such suspicious presentations.