Dear Doctor: I have been diagnosed with chronic inflammatory demyelinating polyneuropathy, and am being treated with immunoglobulin infusions every three weeks. My questions are: Can this be cured, and are there any clinical trials for this?
Dear Reader: You have both my sympathy and my encouragement to seek the best treatment options for you. Chronic inflammatory demyelinating polyneuropathy was first named as a disease in 1975. Caused by the immune system's attack -- for unknown reasons -- on nerve fibers, CIDP affects between one and eight people out of 100,000. The attack upon the muscle nerves in the arms and legs leads to symmetrical weakness throughout the body.
The symptoms of CIDP can progress, or come and go, for more than eight weeks, which differentiates the disease from the more short-lived type of polyneuropathy seen in Guillain-Barre syndrome. About 30 percent of people with CIDP recover fully; but for some, symptoms can progress for years and lead to significant disability, such as an inability to walk.
The treatment that you are getting for CIDP, intravenous immunoglobulin (IVIG), is a concentrate of donor antibodies infused every three weeks after the initial dose. Not only do these antibodies have an anti-inflammatory effect, they neutralize the autoimmune antibodies so they don't attack the nerve cells. Although an estimated 54 percent to 75 percent of patients respond to IVIG, the majority must continue to receive the therapy indefinitely. This can be difficult, causing headaches, nausea, fever and rash, and increasing the risk of meningitis and blood clots.
On the plus side, newer formulations of immunoglobulin -- given subcutaneously -- are showing similar benefit as the intravenous form and can help patients avoid hospital-based infusions.
Some patients fare better on older therapies. One of the first treatments for the symptoms of CIDP were anti-inflammatory steroids, used even before the disease was an official diagnosis. The steroids are administered first at high doses and tapered to lower doses. However, during the tapering, many patients have a return of symptoms and thus must continue the therapy for many months. The problem with chronic steroid use is that it can cause weight gain, diabetes, cataracts, osteoporosis and high blood pressure.
Plasma exchange is another option. This therapy removes fluid containing harmful antibodies from the blood and replaces it with a substitute. The results of plasma exchange appear similar to those of IVIG. Although symptoms return when therapy is stopped, plasma exchange can be a good short-term treatment.
As for immunosuppressant drugs like azathioprine, mycophenolate, cyclophosphamide and methotrexate, these are used more rarely for CIDP. They appear to improve symptoms, but more data are needed on effectiveness, balanced against their possible side effects. Cyclophosphamide may be a good option for people for whom IVIG, steroids and plasma exchange have not helped. But because cyclophosphamide may induce life-threatening side effects, such as bone marrow failure, kidney failure and congestive heart failure, it's not to be taken lightly.
A newer CIDP drug, Natalizumab, which suppresses the immune response against the nervous system, could yet offer hope, but it's still under investigation in Europe.
I would assume that the immunoglobulin therapy is helping you currently, so consider asking your doctor about a clinical trial of the subcutaneous version. This may add convenience for you, without a reduction in benefit.