DEAR DR. DONOHUE: My 48-year-old son-in-law has been told he probably has Charcot-Marie-Tooth disease. We were told there is no definitive test for it. He was adopted, so there is no access to a family history. His symptoms are loss of feeling in both feet and tingling in the fingers. Do you know of a test that might make the diagnosis more conclusive? – L.I.

ANSWER: Charcot-Marie-Tooth (the names of three 19th-century doctors) disease is one of the most common inherited nerve diseases. It affects one in every 2,000 to 2,500. If you divide those figures into the population of North America, you have a large number of people.

CMT is not one illness. It’s a group of illnesses with somewhat-similar signs and symptoms but often different patterns of inheritance. The most common form usually begins before age 20 and starts as weakness in the feet and lower legs. The first warning sign is often constant tripping, because the leg muscles are too weak to lift the feet off of the ground. In addition, the feet often have high arches. Tingling and burning sensations might be felt in the feet and toes. Later on, the process can involve the hands and forearms. As the illness progresses, reflexes – the body’s reaction when tendons are tapped with a rubber hammer – are absent.

There are special tests for CMT. Nerves can be checked for their transmission of electric impulses. Genetic tests are available and are most helpful in establishing the diagnosis.

Although the illness progresses, it usually does so slowly, and it does not shorten life. There is no medicine that stops it in its tracks. Occupational therapists have a variety of aids that make life more livable for CMT patients.

Your son-in-law and all CMT patients should contact the Charcot-Marie-Tooth Association at 1-800-606-2682 for the latest information on the illness, its genetics and how it is diagnosed. The Web site is: www.charcot-marie-tooth.org.

DEAR DR. DONOHUE: My blood pressure medicine was changed from a “beta-blocker” to a “calcium-channel blocker.” What are these blockers blocking? – R.V.

ANSWER: Calcium-channel blockers block the entrance of microscopic amounts of calcium into the ring of tiny muscles that encircle arteries. That muscle ring constricts arteries when calcium tells it to do so. The constriction raises blood pressure.

In people with high blood pressure, the constriction is chronic, and relaxing the muscles by blocking calcium dilates the arteries and lowers blood pressure. For the worried, calcium-blockers do not block calcium’s entry into bones. Norvasc, Cardene, Cardizem, verapamil and Calan are names of some calcium-channel blockers.

Beta-blockers block the transmission of beta nerve signals to arteries with the same effect. The blockade permits arteries to dilate. Pressure drops. Names of some beta blockers are Toprol, Inderal, timolol, metoprolol, nadolol and Coreg.

Beta-blockers are used for many reasons other than for blood pressure control. So are calcium-channel blockers.

The blood pressure booklet presents a complete discussion of this topic. Readers can order a copy by writing: Dr. Donohue – No. 104, 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: How do you get elevated liver enzymes down? – D.O.

ANSWER: Enzymes are proteins inside cells that speed cell chemistry. A rise in blood levels indicates cells have been injured. You get the level down by addressing whatever is injuring liver cells. On your own, there is little you can do aside from avoiding anything that has the potential to harm the liver — alcohol, for example. Your doctor needs to talk to you about this. Call him or her.

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