DEAR DR. DONOHUE: My son is being treated for Guillain-Barre, which affects the nervous system. However, there is a chance of paralysis. Please explain why it takes so long for recovery. I’ve been told it can come from the flu shot. He never had the shot. He is 64, and too young for this kind of illness. — J.S.

ANSWER: Your son is neither too young nor too old for Guillain-Barre  syndrome. It happens at all ages. My nephew had it when he was 19. More than 3,500 cases happen yearly in Canada and the United States. It begins with peculiar sensations in the feet. Then the legs become weak. The weakness creeps upward, and, if it reaches the breathing muscles, the patient must be put on a ventilator.

The immune system attacks myelin, the insulating cover around nerves. Nerve signals are short-circuited. They can’t reach muscles, and that causes weakness and paralysis. Patients often complain of deep muscle pain, and the heartbeat might slow or speed up.

Frequently, GB follows on the heels of an upper respiratory illness (a common cold, for instance) or a nondescript digestive tract illness, which many call intestinal flu. One bacterium, in particular, Campylobacter, which brings cramps and diarrhea, often is responsible for the illness that precedes GB.

Fortunately, most recover fully in weeks to months. It takes time for the myelin covering of nerves to regenerate. A small number of people are left with permanent muscle weakness, and an even smaller number die from it. One of the standard treatments is intravenous immune globulin, IVIG (what is popularly called gamma globulin).

The influenza (flu) vaccine’s connection to GB occurred in 1976, when there was an outbreak of swine flu. The government instituted a campaign for universal immunization. In the early weeks of the campaign, it was noted that more immunized people were coming down with GB than unimmunized people. Since then, flu vaccine has not been associated with even a slight increase in GB illness.

DEAR DR. DONOHUE: My 64-year-old son-in-law had a heart attack. He smokes like a chimney. The doctor told him to quit smoking, and he agreed. However, he has not quit. He says that if he stops smoking, he will balloon up in weight. He also said that it hasn’t been proven that smoking causes heart attacks because people who do not smoke get them. Do you have any rebuttal to my son-in-law’s beliefs?

ANSWER: Your son-in-law is delusional. Mountains of evidence show that cigarette smoking plays a huge role in artery hardening and in heart attacks. He’s denying evidence that reliable scientists have demonstrated to be true, and they have no vested interest in saying this. Other factors also enter the picture — high blood pressure, high cholesterol and genes. A few people have gone over Niagara Falls without dying. Would he like to try that?

As for weight gain, some, but not all those who give up smoking, gain, on average, five to 10 pounds. He’s not going to balloon up.

TO READERS: Back pain is an issue for many people. The booklet on it explains its treatments, and how it can be approached without surgery, many times. To obtain a copy, write: Dr. Donohue — No. 303, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: This may sound silly, but it is a serious question.

As someone who has taught secondary school for many years, I often have wondered if there is a medical reason to explain why most males between 15 and 18 invariably have their mouths hanging open even when they are not eating or talking. Has it got something to do with growth spurts? Why isn’t this as common with females? — C.H.

ANSWER: I haven’t a clue. I never noticed male teenage jaw slackness. I appeal to the public for an answer.

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.