I have been diagnosed with benign mucous-membrane pemphigoid. I continually get sores or blisters on my gums, which keep recurring in the same places. I am currently taking methotrexate once a week. Can you tell me more about this disease?

P.

Benign mucous-membrane pemphigoid, also known as cicatricial (scarring) pemphigoid, is a chronic condition in which blisters form on the mucous membranes, or mucosa. Oral mucous membranes are the most commonly affected, but the mucosa covering the outer surface of the eyes and the inner surface of the eyelids (the conjunctiva), the nasal cavity, throat, esophagus and vagina may also be affected. Conjunctival pemphigoid is the most alarming form of the disease, since (untreated) it can lead to blindness. Conjunctival pemphigoid occurs in about 25 percent of individuals who have oral cicatricial pemphigoid.

Cicatricial pemphigoid is an autoimmune disease. As you delve into this topic, you will find that most authors adopt a very militaristic air when they write about the immune system. That's because the bellicose metaphor works so well for this topic!

The immune system is an army with one mission, to seek out and destroy foreign elements, be they viruses, bacteria, fungal spores or even inanimate objects (such as a splinter). In some cases, this army's mission is somewhat blurred. Cancers are not exactly foreign, inasmuch as they arise from our own tissues, yet it is widely assumed that the immune system actively tries to find and neutralize cancers as they arise. In the case of autoimmune disease, the army has completely and thoroughly screwed up its mission, attacking "self" tissues when it is supposed to be focused on "non-self" invaders.

In one form of diabetes, the immune system destroys cells in the pancreas that produce insulin. In multiple sclerosis, the target is myelin (the "insulation" that coats nerves) in the central nervous system. In rheumatoid arthritis, the joints are targeted. Each of these is an example of an autoimmune disease.

Autoimmune diseases are notoriously difficult to treat. Treatment is necessary only if the disease is a threat to life, limb or function. In the case of cicatricial pemphigoid, concern for possible eye involvement may have motivated your doctor to place you on medication. Autoimmune diseases are sometimes treated with potent anti-inflammatory drugs -- corticosteroids, such as prednisone (Deltasone) or methylprednisolone (Medrol) -- or with cancer chemotherapy drugs such as methotrexate (Rheumatrex).

Why use cancer chemotherapy drugs? Such drugs kill cell types that are actively dividing, such as cancer cells -- and, unfortunately, hair cells, bone-marrow cells and cells that line the gastrointestinal tract. Thus, the common side effects of chemotherapy are hair loss, nausea and bone marrow suppression. Bone marrow is the source of new blood cells. (Continuing the military metaphor, think of bone marrow as blood-cell boot camp.) Chemotherapeutic drugs suppress (retard the growth of) bone marrow cells, thus suppressing the immune system.

Not surprisingly, this is a tricky form of therapy. Undertreat, and the drug may have little or no effect. Overtreat, and the patient may succumb to any of a number of rare diseases that prey upon immunosuppressed individuals (as happens in patients with AIDS). In my opinion, the undisputed masters of this sort of therapy are medical specialists called rheumatologists. You should probably confer with a rheumatologist to find out whether there are any new treatments available for cicatricial pemphigoid; I'm sure a rheumatologist could also answer any other questions that you may have about this uncommon illness.