DEAR DR. DONOHUE: My son, 25, contracted a food-borne bacterial infection this summer in Egypt. As a result, he came down with reactive arthritis. It also has affected his eyes. Tests revealed that he has a gene from his German heritage that caused this arthritis. Will he heal from this? We’ve heard only 30 percent do. – C.W.

ANSWER: Reactive arthritis is a curious kind of arthritis that’s triggered by an infection not in the joints. The infection is either an intestinal infection from germs with names such as Salmonella or Shigella, or a genitourinary tract infection from the Chlamydia germ. Joints “react” to the infection one to three weeks later. The eyes and skin also can be involved.

Most often, one or a few joints swell and become painful, and those joints usually are the knees, hips, ankles and feet. Sometimes patients have low-back pain or heel pain at the point where the Achilles tendon inserts.

The course of the illness is unpredictable, but the majority are better in six months.

Anti-inflammatory medicines like naproxen or indomethacin usually quiet the inflamed joints, and, if need be, cortisone drugs are prescribed.

The “gene” you mention isn’t one limited to people of German ancestry. It’s one of many genes that imprint identification tags on all body cells. In your son’s case, the tag is HLA B27. People who have this ID tag are more prone to develop reactive arthritis, but the illness in them is no more severe, nor does it last any longer than it does in other people.

DEAR DR. DONOHUE: A little more than a year ago, I had X-rays that demonstrated arthritis at the base of the thumb. I had a cortisone shot and wore a special wrap at night. I saw the nurse practitioner two weeks ago, and she said more bone was rubbing together. I had another cortisone shot, this time in the right thumb.

I also notice that in the palm of my hand there are bumps, and my fingers are turning downward.

Is there a name for this condition? Will I lose the use of my hands? – J.K.

ANSWER: Osteoarthritis – the most common kind of arthritis, the kind where bone rubs against bone – frequently strikes the base of the thumb. It’s treated in the same way that osteoarthritis of any other joint is treated – heat, physical therapy, nonsteroidal anti-inflammatory drugs and sometimes cortisone injections.

Your other problem appears to be Dupuytren’s (due-pwe-TRAHNS) contracture. Nodules form on the tendons in the palms, and strands of scar tissue encircle the tendons. Those strands draw the fingers down toward the palm. The ring and little fingers are most often the victims. The process progresses slowly. You might retard its progress by gently stretching the fingers. Put one hand on a table, palm down with fingers extended, and with gentle pressure from the other hand, flatten the fingers. Cortisone injections also have been used for this condition. If the finger or fingers become locked in the bent position, surgery can free them.

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.