DEAR DR. DONOHUE: You just answered a question about emphysema from a man who smoked all his life. I have a friend, in his 40s, who has emphysema and says he never smoked one cigarette. Is this possible? He says it runs in his family. – K.C.

ANSWER: There is no argument. Smoking is the No. 1 cause of emphysema. There are, however, nonsmoking causes, and at least one is inherited. That condition is alpha-1 antitrypsin deficiency.

Emphysema is a destruction of the air sacs, those delicate structures through which oxygen must pass to enter the blood. Trypsin is the lung’s janitorial service. It is an enzyme that keeps the air sacs clean. Left to its own devices, trypsin gets carried away and begins to scrub the air sacs with such gusto that it damages them. The body has a defense for this overzealous cleanup. That happens to be another enzyme, alpha-1 antitrypsin. It stops the trypsin enzyme from carrying its cleaning function to the extreme.

People who have a deficiency of alpha-1 antitrypsin come down with emphysema at younger ages than do smokers. They begin to show signs of emphysema in their 40s. If they smoke, they develop it in their 30s. This is a gene-linked disease, and it is somewhat rare. Only 3 percent, at most, of emphysema patients have the deficiency.

The deficient enzyme can be given to these patients by injection into a vein. The treatment is quite expensive. Not everyone with the deficiency needs it. Some are so mildly affected that their emphysema does not interfere with their lives.

Emphysema and its twin illness, chronic bronchitis, are discussed in the pamphlet on chronic obstructive pulmonary diseases. Readers can obtain a copy by writing: Dr. Donohue – No. 601, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: My fingernails have become as brittle as cheap glass. I cannot blame it on aging, since I am only 39. Could it be a sign of something serious going on in my body? What can I do to strengthen my nails? – D.N.

ANSWER: Brittle nails are a sign of illness in only a small number of people. Thyroid malfunction and anemia are two examples where the nails become brittle secondary to an illness. For most people, brittle nails come from the ravages of subjecting them to repeated immersion in strong detergents.

If you have to submerge your hands into water many times, wear rubber gloves whenever you do.

Don’t use nail-polish remover.

Do keep the nails moist by applying a light coat of petroleum jelly or alpha hydroxy acids frequently during the day. Two brand names of products that have alpha hydroxy acid are DermaNail and Neutraceuticals Nail Lotion.

Biotin, one of the B vitamins, has been hailed by some people as being the answer to their brittle nails. The exact dose is disputed, or I would give you an amount.

DEAR DR. DONOHUE: You told a woman not to worry about her cold sore even though her wedding was upcoming. You missed an opportunity. Kissing can spread the virus, and sometimes people transfer the cold sore virus to the genital area. – S.L.

ANSWER: The woman was concerned that her fiance would think she had a sexually transmitted illness, and she was contemplating delaying her wedding because of her cold sore.

Cold sores are caused by the herpes-1 virus. Genital infections are caused by herpes-2 infections. There are occasions when the herpes-1 virus causes genital infections and the herpes-2 virus causes cold sores, but those instances are few.

People with cold sores should not kiss others. I hope that common sense would keep people from doing so without formal warning. Most of the adult population has been infected with herpes-1 virus, and I did not want this woman to postpone her wedding because of an irrational fear.

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.