DEAR DR. DONOHUE: How can 4 million people have Sjogren’s syndrome and many physicians, dentists and other professionals not know about it? Why has the average person never even heard of it? Please let people know that this disease exists. – D.T.

ANSWER: Most professionals know Sjogren’s (SHOW-grins) disease. It’s not an oddity to them. Few people are familiar with it because it has a strange name and because many of those who have it keep quiet about it. Furthermore, many who have it don’t know they have it.

Sjogren’s consists of dry eyes, dry mouth and often arthritis. It happens more to middle-aged women than to anyone else, but it can strike at any age and to either gender.

Mouth and eye dryness usually progress slowly, so at first people pay little attention to either. However, when symptoms are more pronounced, people cannot ignore what’s happening. They find it hard to swallow food and to talk. The mouth and tongue burn. Tooth decay becomes rampant. The eyes feel like they have sand in them. They burn or itch. Usually they’re red.

About half of Sjogren’s patients have arthritis that most often affects the same joints on both sides of the body, and most often those joints are in the hands, the knees or both.

Many other organs and tissues can be involved. A dry cough is a sign of lung involvement.

Sjogren’s is an autoimmune disease. The body has lost its ability to distinguish foreign tissue from its own tissue and sets about attacking its own tissues.

Lymphocytes – one of the white blood cells, and one that is involved with immunity – infiltrate the salivary and tear glands and stop the production of saliva and tears.

Artificial tears – Tearisol, Liquifilm Tears and 0.5 percent methylcellulose – can keep eyes moistened. A newer eyedrop, Restasis, has proven useful to many. Artificial salivas do the same for the mouth. Numoisyn liquid and lozenges are the newest additions to the list of such products. Pilocarpine (Salagen) and cevimeline (Evoxac) are pills that promote saliva production.

Your wish has been fulfilled by the Sjogren’s Syndrome Foundation, dedicated to spreading the word about it and to helping people affected by it. The foundation can be reached on the Internet at www.sjogrens.org or by dialing 800-475-6473.

DEAR DR. DONOHUE: I am a 12-year-old student. My teacher reads us parts of your articles that pertain to what we are studying. She read us the one about a woman with a high platelet count. You said there was no known cure. I asked my teacher why the woman couldn’t donate her platelets to people who need them. My teacher told me to write to you. Have I outsmarted the doctor? – I.C.

ANSWER: Platelets are the blood cells that form clots when a blood vessel breaks. Too many platelets is thrombocythemia. (“Thrombocyte” is another name for “platelet.”)

Some people with a high platelet count don’t need treatment because they don’t have any symptoms. Doctors treat people who have high platelet counts and symptoms with hydroxyurea, anagrelide or interferon.

Platelet transfusions are used in a number of conditions for people with low counts. However, those platelets come from healthy donors. The platelets in people with thrombocythemia are often defective, so they can’t be used for transfusion. Your idea, all the same, is most imaginative, and you can take over for me anytime you want.

DEAR DR. DONOHUE: I am 80 and have arthritis and a bad heart valve. They want to operate. When I walk to get the paper, I am all tired out. Is it the heart valve or arthritis that’s doing it? – K.A.

ANSWER: My money is on the heart valve. Osteoarthritis, the most common kind of arthritis, doesn’t make people tired; it makes them hurt. You’re not too old to have the operation. My mother had it at age 76.

The booklet on heart valves explains what they do and how they can go wrong. To order a copy, write to: Dr. Donohue – No. 105, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: Please explain what these common body functions are: yawn, stretch, itch, stomach noises, burp, snore, sneeze, flatulence and cough. – N.G.

ANSWER: Yawn: No one is sure what its function is. It does not, however, increase the amount of oxygen in the blood, a common explanation for it.

Stretch: a universal reflex to having had muscles in a cramped position or upon wakening from sleep. It relaxes the muscles.

Itch: a response to the release of certain body chemicals that activate nerves that carry signals to brain parts to produce the itch sensation. It’s a bit like pain signals.

Stomach noises (borborygmi – BORE-bo-RIG-my): the splashing noises made by gas churning up fluids in the digestive tract. They serve no useful function other than to draw attention to the person with them.

Burp: relieves stomach distention caused by an accumulation of gas there – the gas is usually air.

Snore: comes from the vibration of air rushing past loose and lax throat tissues.

Sneeze: clears the nose and throat of foreign matter.

Cough: does the same for the airways.

Flatulence (the passage of gas): decompresses the colon of gas formed by bacteria dining on undigested food.

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