Paul Kechijian, M D, is a dermatologist who practices in New York. He is also chief of the nail section and clinical associate professor of dermatology at New York University Medical Center. Dr. Kechijian has written numerous articles and given many presentations on nail diseases and disorders. He is currently writing a chapter on nails for a medical textbook

Because nail technicians see more nails than anyone, they are in an ideal position to detect nail disorders early and refer clients to a dermatologist when necessary. One nail disorder that always should be referred to a dermatologist is longitudinal melanonychia, because it can be an indicator of melanoma, a potentially deadly form of cancer that can be cured if diagnosed and treated early. Longitudinal melanonychia is a pigmented band that runs fro the proximal nail fold to the nail tip. The band, which can be tan, brown, or black, is caused by an increase in melanin pigment in the nail plate. Melanin is the same pigment that determines skin color and allows people to tan.

Although longitudinal melanonychia is not common in people with fair complexions, it is very common in dark-skinned individuals of various ethnic origins, especially people of African, Chinese, Japanese, Indian and Latin descent. Generally, the darker the skin, the more likely a person is to develop longitudinal melanonychia as she ages. In fact, by age 70, almost all black individuals have longitudinal melanonychia.

Not all pigmentary changes of the nails are longitudinal melanonychia. The most common discoloration confused with longitudinal melanonychia is blood collected under the nail plate, called a subungual hematoma, which makes the nail appear black or brown. Subungual hematomas are caused by trauma and are common on the hands and feet.

Being able to make the distinction between pigmentary changes caused by blood and those caused by melanin is obviously important. When brown pigment suddenly appears under the nail following an injury, you can safely assume the disorder is a subungual hematoma, which will grow out with the nail plate, while longitudinal melanonychia will not. If you are uncertain about which is causing a pigmentation change, refer the client to a dermatologist.

Other conditions can simulate longitudinal melanonychia, but are less dangerous. For example some oral medications can cause the nail plate to discolor. Bacteria, yeast, and fungal infections of the nail also cause color changes. Again, if you aren’t sure of the cause of the discoloration, refer the client to a dermatologist.

Although a biopsy of the nail is often necessary to establish the cause of longitudinal melanonychia, careful examination of the nail by a dermatologist can provide important clues to whether longitudinal melanonychia is caused by a benign disorder or melanoma. The presence of more than one pigmented band, for example, is a clue that longitudinal melanonychia is benign (non-cancerous) in origin.

Dark-skinned individuals commonly have more than one band of nail pigmentation. The presence of bands on more than one finger makes the diagnosis of melanoma unlikely because melanoma usually occurs on only one finger. Hormonal disorders, malnutrition, and pregnancy also can cause increased pigmentation in several nails at once, as well as on skin.

If pigmentation spreads to tissues surrounding the nail – the cuticle of proximal and lateral nail folds, for example – melanoma is more likely to be present. A dark-colored band, especially on a fair-skinned person, should be viewed with great suspicion.

Variation in color within the band itself – different shades of tan, brown, or black – can also suggest melanoma, as do blurred, fuzzy, or ill-defined margins between the colored and normal portions of the nail bed. A very wide band that occupies most of the nail is of greater concern than a thin band.

Generally, melanoma occurs in older individuals and tends to occur in the thumb, index finger, or big toe. People in their sixties are most vulnerable, though the frequency of melanoma increases gradually after age 20. Some physicians believe that trauma plays a role in the development of melanoma. If trauma does play a role, injury to the nail may stimulate growth of pigment cells that, in time, could progress to formation of melanoma.

Not every client who exhibits longitudinal melanonychia has melanoma. Longitudinal melanonychia is rare; melanoma is still more so. Awareness of the condition, however, better enables you to evaluate pigment changes in the nails and to advise clients when you think further evaluation is necessary.