DEAR DR. ROACH: After having several strange-looking “pimples” on my thighs and one on my face, I was told it is lymphomatoid papulosis. One or two people in a million are diagnosed with this. I know that it is not contagious, but what is it? What causes it, how is it treated, and what can I do to avoid these? They take weeks to heal. — R.R.

ANSWER: Lymphomatoid papulosis is a rare disease. It is in the category of cutaneous lymphoproliferative disorders. It is a chronic disease, and lasts years or even decades. The underlying cause is not known exactly, but it is related in many ways to other lymphoproliferative diseases, such as mycosis fungoides and Hodgkin’s lymphoma. The cells of the skin lesions you notice have similar genetic rearrangements as lymphoma cells. Fortunately, LyP has an excellent prognosis, although people with LyP are at increased risk for developing one of these serious conditions.

The papules of LyP can appear on the extremities or the hands and face, and less commonly on other places on the body. They may start off as small red papules, get larger and then crust over. Often, several exist at different stages.

Diagnosis may not be easy, as it takes an experienced dermatopathologist (pathologist with special training in skin diseases) and enough tissue to look at the genetics of the cells. Treatment is not necessary for every person with LyP. But for those who do require it, one might be ultraviolet-light treatment. More severe cases may require methotrexate, but this needs to be managed by an expert.

Experts have recommended six-month visits to evaluate for early signs of enlarging lymph nodes, which might indicate the development of a lymphoproliferative disorder.

DEAR DR. ROACH: Last year, my husband was seriously ill from a bacterial infection in his gallbladder. After inserting a drainage tube, they removed his gallbladder. He has done quite well, except for a strange side effect: Whenever he eats, it causes his left shoulder to hurt. Also, when he lies on his right side, it seems to hurt his left shoulder. Do you have an explanation for this mystery? — L.F.

ANSWER: I have a possible explanation. The pain nerves to your skin and bones are referred to as parietal pain fibers, and these localize very well: If your left toe hurts, there’s usually a problem with your left toe. The nerves to the organs are visceral fibers, and they do not localize well in the brain. Pain in the heart can feel like it’s in the left upper arm, the left side of the chest or the upper abdomen, depending on who you are. Pain from the gallbladder most commonly shows up in the right upper quadrant of the abdomen, where it is located directly under the liver, but frequently feels like it is coming from the shoulder. This is called “referred” pain. Right-shoulder pain is more common than left, but I still think that your husband is feeling some referred pain, perhaps from some scar tissue.

DEAR DR. ROACH: Can skim milk or oat bran cause gas? — J.R.

ANSWER: Both certainly can cause gas. Skim milk contains the milk sugar lactose, to which many people are intolerant. In mild cases, it causes some gas; severe cases can cause diarrhea. Oat bran is a good fiber source, and all good sources of fiber can cause gas, especially if taken in amounts that are greater than the person is used to.

The booklet on constipation explains this common disorder and its treatments. Readers can order a copy by writing: Dr. Roach — No. 504, 628 Virginia Dr., Orlando, FL 32803. Enclose a check or money order (no cash) for $4.75 U.S./$5 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.