DEAR DR. DONOHUE: My 52-year-old son has Creutzfeldt-Jakob disease. Can you tell me something about it? Is it genetic? Can it be dangerous to people who come in close contact with him? He has four children. Are they in danger? – J.S.

ANSWER: Creutzfeldt-Jakob disease is uncommon, occurring in one person out of every million. Its tangled story has not been completely unraveled, but the essentials are as follows.

The most frequent kind of C-J disease is called sporadic. It’s an almost exclusively adult illness, usually affecting people between the ages of 40 and 70. Its outstanding feature is progressive loss of mental functioning similar to what happens in Alzheimer’s disease. Initially, the only signs might be trouble sleeping, fatigue and vision disturbances. Memory and thinking then begin to deteriorate. Loud sounds often cause C-J patients to have an exaggerated startle reaction.

The cause is a prion – a protein that is a recent discovery and a most unusual life form. It has no DNA, something every other living organism has. Even though the protein replicates, it is not passed from one person to another. Your son most likely has sporadic C-J disease. Neither his children nor those who come in contact with him are in danger.

Variant C-J disease is another version of the illness. It’s believed to come from eating the meat of cattle that had mad cow disease. This variety of C-J happens to a younger population. The average age of onset is 26.

Finally, there is a familial form of the illness that also appears at younger ages. The tip-off that a family influence is at work is a history of other family members having been stricken with it.

DEAR DR. DONOHUE: I am a senior citizen who has developed what doctors say is a stomach hernia. I have had an unsightly bulge on my left side for the past two years. It doesn’t hurt, but it can be uncomfortable. What is a stomach hernia? What caused it? Is there something I can do to get rid of it? The doctor tells me to wear a tight girdle, and it won’t increase in size. How could the doctor know this is a hernia without having done any X-rays? – M.M.

ANSWER: In everyday speech, “stomach” is used for “abdomen,” the body region that contains the liver, the pancreas, the stomach and the intestines. The stomach is the hollow sack that receives swallowed food. Your hernia, in anatomically strict terms, is an abdominal-wall hernia.

All hernias are protrusions of inner organs or tissues through a defect in the wall that is supposed to keep them in place. In your case, the wall with the defect is the abdominal muscle. There’s a weak spot in it, and abdominal tissues are protruding through it to create a bulge. It’s a situation very much like an inner tube sticking through a hole in a tire.

If an abdominal bulge flattens out when a person lies down or if the doctor can gently finesse the bulge back into the abdomen, then the odds are great that the bulge is a hernia. No X-rays are needed.

Short of surgery, there is nothing you can do to get rid of it. A girdle will hold it in place but won’t eliminate 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.