DEAR DR. DONOHUE: My granddaughter has cystic fibrosis. We were informed that it is a fatal disease. She is 4 months old and receives high potency vitamins, salt and enzymes. What causes it? What are her chances of living a normal life? We have to wash and disinfect our hands before coming in contact with the baby. How long will she live? – H.W.

ANSWER: Life is a fatal disease. We’re all programmed to die. Cystic fibrosis shortens a person’s life, but not to the extent it did only a few decades ago. The life span of an infant with cystic fibrosis is difficult to predict, but I know a young man with cystic fibrosis, in his 30s, who has had a lung transplant, is married and holds down a 40-hour-a-week job as an accountant.

Cystic fibrosis is an inherited illness. Both mother and father, neither of whom has symptoms, give the baby a gene for it.

It has an impact on many organs, but the two principal ones are the lungs and the pancreas. Glands of the airways secrete thick, copious mucus that impair air passage into and out of the lungs. The secretions can be so thick that they form plugs that block the airways. The airways and lungs of a cystic fibrosis patient are highly susceptible to infection, and that’s why care must be taken in controlling the baby’s contact with people.

The pancreas has two functions. One is that it produces enzymes that digest food. Your granddaughter’s prescribed enzymes are ones that now break down food for her. The pancreas also makes insulin for blood sugar control. Cystic fibrosis interferes with insulin production in about 7 percent of patients, who then become diabetic.

Salt is necessary because excessive amounts are lost in CF patients’ sweat. Salty sweat gives rise to one of the famous signs of this illness — kissing a CF baby imparts a salty taste.

Gentle chest pounding along with positioning the baby to promote drainage of secretions keeps the airways clear. Lung infections must be treated quickly. Digestive enzymes permit normal growth. The possibility of a lung transplant down the road is a new approach in treatment. You and your daughter ought to get in touch with the Cystic Fibrosis Foundation for the latest information in treatment and for locating support groups. Its Web site is www.cff.org.

DEAR DR. DONOHUE: I was diagnosed with asthma as a child. I am now 33. I am active, in good health and exercise five or six days a week. I use my asthma inhaler about twice a month. I wheeze maybe every other day but don’t need medicine. My doctor thinks I should use daily medicine. I don’t wish to start. Will I damage my lungs if I don’t? – J.F.

ANSWER: Asthma consists of recurring episodes of airway-narrowing with inflammation of the airways and an outpouring of airway secretions. The result is difficulty getting air into and out of the lungs. If asthma isn’t restricting a person’s life, if the person has near-normal lung function and if asthma is not disrupting sleep, then that person can take asthma medicine on an “as needed” basis without damaging the lungs. Talk with your doctor again. If you need proof of your lungs’ health, get some lung-function tests done. They need not be elaborate or expensive.

The asthma pamphlet discusses all aspects of this illness. Readers can order a copy by writing: Dr. Donohue – No. 602, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 US/ $6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: Just as I am dropping off to sleep, I will jerk and wake up. What is this? – N.R.

ANSWER: Such jerks are normal and have a name – hypneic jerks. Often, they don’t wake people, so they can go undetected. When the brain is in a transition between sleep and wakefulness, it can momentarily lose control over muscles, with the resulting jerking.

If this disturbs you greatly, cut back on caffeine; you might not experience it anymore.

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