DEAR DR. DONOHUE: I need to know what a Clark’s nevus is. I am 53. In the past year, about 50 spots appeared on my body, and some have been surgically removed. I am fair-skinned. There is no history of melanoma in my family. How do you tell the difference between good and bad nevi? Do good ones change into bad ones? Where did I get this disease? There’s no family history of it. They seemed to appear after I started coloring my hair. Does hair dye cause them? Am I at higher risk of getting melanoma? Will I die from this? — D.P.

ANSWER: In this situation, a nevus is a mole. Most moles are harmless. A Clark’s nevus is not a cancer, not a melanoma, but it has a small potential to become one. It has other names: atypical nevus and dysplastic nevus. Atypical is the name most commonly used. It’s not unusual. Between 2 percent and 10 percent of the white population has one or more. You are not alone.

A family trait is one cause of an atypical nevus. Prolonged exposure to sunlight, especially during childhood, is another factor for developing atypical nevi. A large number of them also is a risk for melanoma to evolve. Hair dye has nothing to do with them. Atypical nevi can be difficult to distinguish from melanoma. They have some of the characteristics of a melanoma. They might have a fuzzy border; a harmless mole has a distinct border. They often have a mix of colors — reds, tans, browns and blacks. Most harmless moles are smaller than the diameter of a pencil’s eraser; atypical nevi can be larger. One very helpful way in determining if an atypical mole is becoming cancer is the “ugly duckling” sign. If an atypical nevus looks quite different from other moles on the body, it should be viewed with great suspicion. Any mole that changes rapidly in size, color or border is another sign of danger.

I understand from your letter that you have had doctor troubles in the past with your nevi. Find a dermatologist you relate well to. Let that doctor examine you every year or every six months. You can do a self-exam every month. The rest of the time, don’t dwell on this. You are not likely to die from an atypical nevus.

DEAR DR. DONOHUE: About 60 years ago, my friend died from multiple sclerosis. At the time, I was told that the nerve lining, myelin, had deteriorated and caused the illness.

I just read in your column that Guillain-Barre syndrome is an illness where myelin also deteriorates. Is there a connection between multiple sclerosis and Guillain-Barre syndrome? — P.H.

ANSWER: Myelin is insulation for nerves. Without myelin, transmission of nerve signals is short-circuited.

A long list of demyelinating diseases exists. Multiple sclerosis and Guillain-Barre are on that list. That is the only connection between the two.

Demyelination in multiple sclerosis takes place in the brain and spinal cord.

Demyelination in Guillain-Barre takes place in body nerves that transmit information to muscles and organs. They are two quite different illnesses, with different signs, symptoms and treatments.

DEAR DR. DONOHUE: I read with interest your “Fainting Is Not a Sign of Serious Problems.” I had a series of faints in 1998 and was told that they were just faints. Then I fainted again. I was sent to an electrophysiologist, who identified the problem as intermittent atrial fibrillation. I was treated for it and haven’t had a faint since. — E.B.

ANSWER: The headline should have been, “Fainting Not Usually a Sign of Serious Problems.” Faints can and do occur from abnormal heart rhythms.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.

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