DEAR DR. DONOHUE: My next-door neighbors had a large family, with seven grown children. Three died of Lou Gehrig’s disease. I have asked my doctor about this, and he said that it is not inherited. How else can you explain this family’s situation? Is there a test for the disease, and is there any treatment? Please tell me about this illness. – P.M.

ANSWER: Lou Gehrig’s disease is inherited in only about 5 percent to 10 percent of its patients. Your neighbors must be among that small percentage. The medical name for the illness is amyotrophic lateral sclerosis, or ALS.

There is a test to detect inherited Lou Gehrig’s disease, but it is not foolproof. If the test comes back positive, that is strong evidence that the tested person will come down with the condition. If the test comes back negative, however, that is not proof that the tested person will not have the disease.

The chance that a child of a Lou Gehrig patient will have the disease is one in two.

Muscle weakness is the hallmark sign of this illness. That might not manifest itself until people are in their 50s and 60s. At its start, muscle weakness might only be regarded as clumsiness in walking or using the arms. Weakness progresses, and people eventually are wheelchair-bound. Vocal cord muscle involvement impairs speech, and throat muscle involvement impairs swallowing. When breathing muscles are affected, as they almost always will be at some stage, drawing air into the lungs becomes difficult or nearly impossible. Patients end up as prisoners in their own bodies.

Rilutek is a medicine that can slow the progression of this illness, but it is not a cure.

All ALS patients and their families ought to get in touch with the Amyotrophic Lateral Sclerosis Association for information on the illness and for practical ideas on how to cope with it. The number is 1-800-782-4747, and the Web site is www.alsa.org.

DEAR DR. DONOHUE: Would you explain erythema nodosum for me and others? I take prednisone for it. It disappears as long as I take medicine, but it comes back when I stop. – J.H.

ANSWER: Acute erythema nodosum comes on suddenly and consists of red bumps that can be tender and painful. They most often appear on the lower legs. In addition to the skin outbreak, people feel dragged out, and their lower legs can swell. Joint pain is also common.

Sometimes a strep infection precedes the outbreak. Other infections have also been implicated. Fungal infections, for example, trigger it. So can medicines, the birth control pill being one example.

Chronic erythema nodosum follows a slightly different course. It targets older women, but not exclusively. The skin outbreak is similar, and it too can be associated with an underlying illness, but not as often as the acute form. The chronic form can last months or years.

If an underlying illness can be found and treated, that generally takes care of the problem. If no associated illness is found, then treatment is a bigger problem. Prednisone, one of the cortisone drugs, suppresses the skin bumps, but, as you have said, they can recur when the medicine is stopped. Potassium iodide can sometimes control outbreaks.

If you haven’t tried it, it might eliminate this pesky, difficult condition.

DEAR DR. DONOHUE: Eight months ago I had a miscarriage. Since then, I have had only two menstrual periods. Most bothersome is the pain I have after sexual relations. At first it was just cramping. Now I feel like my insides are ripped out, and I end up in the fetal position for hours. I have also acquired thick, black facial hair. Do you have any ideas? – U.A.

ANSWER: You must get to a gynecologist immediately. I cannot wrap all these major symptoms in a neat package for you, but they demand an examination right away. All of them could be related to your miscarriage. Delay in finding a cause will delay the cure for it.

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.