QUESTION: This regards your recent item on mumps. I am a retired physician, 78. I interned at Tacoma (Wash.) General. As an intern, I walked into the room of a rough-tough attorney. He was sitting up smoking a cigar (against regulations, of course), and he immediately said to me, "Well, doctor, I'll bet you don't know what I'm in the hospital for." I said, "Mr. -, I haven't seen your chart, so I don't know what your admitting diagnosis was, but I see you have Mikulicz's disease" - cocky, smart-aleck intern that I was - and my diagnosis was correct. Never saw a case again, although I never ceased my search. Enjoy your straightforward attitude and words. You do a laudable job representing us. I've been retired nine years, play golf and yes, I drive a Buick. Am I a stereotype? - G.H.B. MD

ANSWER: Even though you golf and drive a Buick, you are not a doctor stereotype. You are at least as rare as Mikulicz's syndrome.Dr. B refers to my reply to an older woman reader who swore she had mumps as a child and reported a second encounter at age 69. I offered some non-mumps causes for swelling of the parotid glands. Those salivary glands are prime mumps virus targets, causing the characteristic cheek swelling.

However, when those glands become inflamed for any reason, the same swellings occur. In my abbreviated answer, I did not mention Mikulicz's syndrome, parotid gland swelling along with fever and dry eyes caused by eye gland inflammation. Mikulicz's is sometimes part of more general illnesses, like TB, leukemia, Hodgkin's disease or lupus. It is something to consider, although, as the Sherlockian Dr. B. says, it's pretty rare.

QUESTION: I have written before. Is it that my health problem (Baker's cyst) is not serious enough for your column? - M.D.M.

ANSWER: Not at all. I discussed Baker's cyst a few months ago in answer to another writer. Perhaps you missed that.

A Baker's cyst is a bursa behind the knee. This fluid-filled sac connects to the knee joint via a narrow tunnel with a one-way valve to permit fluid to escape into the bursa, but not out of it. If there is trouble in the knee, excess knee fluid can flow in and be trapped in the bursa. That is your Baker's cyst, named for the doctor who first explained the problem.

Rest and anti-inflammation medicines often allow time for reabsorption of the bursa fluid. If not, cortisone drugs may do the trick. If they fail, the cyst can be drained with a syringe or surgically removed. Always, however, the knee joint must be examined to see if there is some contributing mischief there.

QUESTION: What is the difference between Ativan pills and Triavil 2-10s? - M.K.

ANSWER: Ativan (lorazepam) is a drug for anxiety control, a tranquilizer, if you will. Triavil is a combination of perphenazine, another anti-anxiety pill, and amitriptyline, an antidepressant. The 2-10 identification refers to the fact that the pills have two mg of perphenazine to 10 mg of amitriptyline.

FOR L.B. - I am sorry about your experience with niacin. No substance is entirely risk free. Niacin taken in doses up to 3,000 mg daily is innocuous for most. At very high doses, it can cause liver problems, as it did for you. It can also elevate blood sugar and uric acid, a prelude to gout. But such side effects are usually reversed when you stop taking it. Yours was an unusual case.

Dr. Donohue's material on waistline slimming outlines a five-step program based on the specific muscles involved. For a copy, write Dr. Donohue/No. 38, P.O. Box 830, Gibbstown, NJ 08027-9909. Enclose a long, stamped, self-addressed envelope and $2.

Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.