DEAR DR. DONOHUE: Psoriasis started on my legs about four years ago. Now it has spread to other parts of my body. I know there is no cure, but will you expound on the medicines used to treat this disease? I am 84. – E.J.

ANSWER: Don’t focus on the fact that there is no cure for psoriasis. Focus on the fact that there are a huge number of treatments and, most often, one can be found that keeps the process in check.

Psoriasis can begin at any age. It has been known to start in people who are 100 years old or in the early months of infancy, but it most often arises around age 27.

The immune system, for unknown reasons, speeds up the production of skin cells. Normally it takes a month for newly made skin cells to rise from the deepest layer of skin to the skin surface. In psoriasis, they rush to the surface in a matter of days. The result is a patch of red skin that often is covered with silvery scales. Any part of the body can break out with such patches, but the most common sites are the elbows, knees, palms, soles and scalp.

For many patients, creams and ointments can control psoriasis. Cortisone creams and ointments are often chosen. There are more than 30 different varieties, so finding which is best for a particular person takes time. Dovonex is a vitamin D preparation that comes as a cream or ointment. It is often used in conjunction with a cortisone preparation. Other topical treatments include salicylic acid with tar and Tazorac, a vitamin A relative.

Ultraviolet light – simple sunlight – can be most helpful. Artificial ultraviolet light in conjunction with psoralen drugs is effective for many.

The oral medicine methotrexate modulates the immune system and produces good results. Other orals are Soriatane and tacrolimus.

Three new medicines – Humira, Raptiva and Enbrel – are held in reserve for when none of the many other medicines makes any headway. Your cup of medicines runneth over.

DEAR DR. DONOHUE: I just found out I have ulcerative colitis. How does a person get it? Is it from food, or maybe inherited in a family? – R.N.

ANSWER: The exact cause of ulcerative colitis has yet to be discovered. It’s not directly inherited, as in a parent passing it to children, but there is a genetic predisposition toward developing it. In other words, no single gene is its cause, but some people do have a genetic makeup that renders them susceptible to developing it. That genes have an influence is demonstrated by its high incidence in the Jewish population and low incidence in Asians and South Americans.

The actual activating factor that causes ulcerative colitis to emerge in these predisposed people is only conjectural. It might be a germ that turns on the immune system, which then begins to assault the colon and leads to ulcers on its surface.

No food is believed to be implicated in its onset.

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.