Q. What is Peyronie's disease? Is there any treatment for it? Does it cause impotence?

A. Peyronie's disease refers to dense scarring of a sheath of tissue just below the skin of the penis. The scar tissue feels hard and lumpy, and usually runs in a line on the upper surface of the penis from the base to just before the tip. Many victims mistakenly fear they have cancer. It is an uncommon condition usually affecting middle-aged men. The cause is unknown, but in rare instances may be related to medications such as propranolol (Inderal). If so, the scar tissue clears up when the medicine is stopped.

Peyronie's disease causes erections to be painful; it also leads to abnormal bending of the erect penis that may make intercourse difficult. It doesn't cause impotence, except in the sense that it can make intercourse painful, physically difficult or emotionally stressful.

There is no fully satisfactory treatment for Peyronie's disease, but the disorder often stabilizes or improves with time. In severe cases, a urologist can operate to remove the scar tissue and insert an artificial implant in the penis to aid erections.

Q. I'm six months pregnant with my second child and have had a normal pregnancy so far. My doctor wants to do a sonogram. Is this necessary? I've heard that sonograms can change cell structure and cause miscarriages. Are there risks with a sonogram?

A. Sonograms are very safe and painless procedures, but they should be done for a specific reason. Sonograms, also known as sonography or ultrasound, use sound waves to create images of internal organs on a screen.

It's true that some laboratory experiments have shown that sound waves can disrupt delicate molecular structures inside cells. Some scientists have also cautioned about the theoretical risk of damage to a developing fetus's hearing. Although more studies are needed, to date no reports have linked sonography with birth defects in humans.

Sonograms don't cause miscarriages, either. You're probably thinking of the low risk of miscarriage after amniocentesis (sampling of fluid from the womb to detect birth defects). Doctors often use sonography to help insert the sampling needle. Miscarriages may be a result of the amniocentesis, but not of the sonogram.

Experts at the National Institutes of Health recently issued guidelines on sonography during pregnancy. They specifically recommended against its routine use -- doing sonograms without having any specific reason. My guess is that this recommendation will be relaxed somewhat, and that studies will show that routine sonography is valuable because it identifies important conditions that the physician didn't otherwise suspect. But as with many new techniques in medicine, this procedure is also subject to overuse.

The guidelines approve of sonography in circumstances such as: estimating the age of the fetus and date of delivery; evaluating fetal weight, growth and well-being; diagnosing multiple pregnancies; evaluating vaginal bleeding; diagnosing congenital problems; aiding in amniocentesis; determining how the fetus is positioned in the uterus.

Q. Off and on for several years, I've had cracks in the corners of my mouth. Every time I open my mouth it hurts. I've tried 1,500 milligrams of vitamin C daily, but that didn't help. Chap Stick sometimes helps, but not completely. What causes this and what can I do about it?

A. You're describing something doctors call cheilitis, meaning an inflammation of the lips, which often occurs at the corners of the mouth. It's a condition with several causes, and usually affects older people.

Improper motion or alignment of the mouth structures can lead to cheilitis by causing constant irritation at the corners of the mouth. This can happen with improperly fitting dentures, sagging cheeks, excessive licking of the lips and drooling. In some cases, a candida yeast infection can set in and add to the problem.

Once the fissures form, they can be self-perpetuating, aggravated by chewing, talking, or poking at the sore spot with your tongue.

Good nutrition and oral hygiene are necessary for successful treatment. You can protect the area and allow it to heal by applying petroleum jelly (Vaseline) or zinc oxide ointment several times a day. If the condition doesn't clear up completely, check with your dentist if you have dentures; otherwise, see your doctor. Bear in mind that a sore that doesn't heal could be a skin cancer.