DEAR DR. DONOHUE: I am 50, and last year I was diagnosed with autoimmune hepatitis. I have been on medicine for it. After a few months of normal blood tests, my prednisone (one of my medications) was halved. Now I am being weaned off prednisone completely.

Now that my liver-function tests are normal, does that mean liver damage has stopped? And since I take medicine that blocks the immune system, am I more susceptible to infections? – P.W.

ANSWER: Hepatitis is liver-cell inflammation, and when that word is used, most think of viral hepatitis. The immune system can turn against liver cells and also cause inflammation – that’s autoimmune hepatitis. What causes this to happen is inexplicable at present.

Autoimmune hepatitis can also inflame blood vessels, and the kidneys can be involved. It causes people to feel exhausted all the time. Menstrual periods are often thrown out of kilter.

Treatment is the kind you received – prednisone (a cortisone drug) often coupled with azathioprine to stop the immune attack.

The fact that your liver-function tests are now normal is a good sign and indicates that liver damage is coming to a halt. Your dose of prednisone is a very low one, one that should not weaken your ability to fight off infections.

DEAR DR. DONOHUE: Our son-in-law has been diagnosed with M. avium infection. We would appreciate an explanation and your input in regard to treatment for this problem. He has been informed that there is the possibility of remission because of using strong antibiotics.

My son-in-law has only one lung. – B.K.

ANSWER: Mycobacterium (MY-coe-back-TEER-ee-um) avium is a bacterium widely distributed throughout nature. Exposure to it is quite common. Most people can come in contact with it without coming down with any illness. Up to 40 percent of all the adults in the northern and southern United States have been invaded by the germ, and most have never developed a single sign or symptom. A few, however, do develop an infection, usually a lung infection that produces fever and a cough. Chest X-rays show a pattern typical of infection with this germ.

Finding the bacterium in a person’s coughed sputum presents problems. Is the germ simply there and doing no harm, as it is in many people’s sputum? Or did it contaminate the sputum specimen on its way to the lab? Or does it truly constitute an infection?

The decision is made based on the chest X-ray, the person’s symptoms and finding the germ in three different cultures of the person’s sputum.

If your son-in-law has a true infection, he needs to be treated with three antibiotics. The germ is resistant to the action of only one or two antibiotics. The antibiotics are ethambutol, rifabutin and azithromycin. They are not exceptionally powerful, but they are a potent combination against M. avium.

The germ is a distant relative of the TB germ. Don’t let that upset you. M. avium is not TB and is not spread like TB.

DEAR DR. DONOHUE: My doctor prescribed Plaquenil for my arthritis. Any comment on its safety? – A.R.

ANSWER: Plaquenil has been used since 1955, so there has been great experience with it. No truly unsafe drug would have survived in the marketplace for so long.

Its original purpose was to treat malaria. Now it is sometimes used for rheumatoid arthritis and lupus.

Plaquenil’s most serious side effect is retinal damage. When a person takes the drug, he or she must have regular eye exams. The drug is stopped immediately should there be any signs of incipient retinal damage. This side effect is well-known and carefully watched for, but seldom happens.

DEAR DR. DONOHUE: In your discussion of osteoarthritis, you did not mention glucosamine or chondroitin. I have been taking them for a few years, and I do not notice any change in my condition. Should I continue? – S.B.

ANSWER: Glucosamine is believed to stimulate the growth of joint cartilage, which would be an enormous benefit to those with osteoarthritis. That illness causes joint cartilage to crumble. Its cushioning effect is gone, and bone rubs against bone. Glucosamine is extracted from the shells of shrimp, crabs and lobsters.

Chondroitin is said to keep joint cartilage supple and resilient, another boon for those with osteoarthritis. It comes from animal and shark cartilage.

To date, studies make contradictory statements about the effectiveness of these two substances. The National Institutes of Health is in the midst of a large study evaluating their usefulness. The results should be published in the fall.

You have conducted your own personal study. These products haven’t benefited you. They’re not likely to do so with further use.

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.