Monday, November 10, 2008

Peripheral Neuropathy Associated with Gammopathy

Peripheral neuropathies are not that rare, the most common cause being Diabetes Mellitus. I have had a neuropathy for 25 years and until recently its cause to me was unknown. The fact that it appeared to be progressing since the beginning of this year prompted me to have it investigated further.

In 1983 I noticed slight numbness on the sole of my left foot. I had been running, using just my forefeet, not the usual heel-to-toe landing, because of a painful knee subsequent to a leg fracture. This running style cushioned my landing and muted pain in the knee. I attributed the numbness to the pounding from running 40 plus miles every week. Then in 1984 numbness appeared in my right sole, too, which made it unlikely that running was the cause.

I saw a neurologist at that time and he did the usual EMG and nerve conduction studies (NCS) which were completely negative. Blood studies were also unrevealing. I didn’t have diabetes, I had no family history to suggest a genetic basis for the disease, I drank little that might suggest an alcoholic basis and the blood studies ruled out heavy metal and other poisonings. I was diagnosed with a neuropathy of unknown etiology. I had no further investigation for some time thereafter. I continued to run high mileage for the next 6 years and I noticed no significant progression of the numbness which was my only symptom

In 1999 I developed Polymyalgia Rheumatica (PMR), a muscular disease, which in my case involved pain in the muscles of the shoulder girdle. This was quite severe but fortunately it responded to a course of steroids (Prednisone). It persisted to a low degree for a year and then cleared completely. However, during that year I noted onset of slight numbness in the fingers of both hands. I checked the literature and discovered that this could occur with PMR so I did not have it investigated. Now in 2008, some 25 years from first onset, I noticed that the numbness in my fingers was progressing which finally prompted me to see a neurologist.

I had both an EMG and NCS and this time the latter was abnormal, showing damage to both the myelin sheath (covering of the nerve fiber or axon) as well as axonal damage, both in my feet and hands. My neurologist thought this unusual to see both types of damage so she referred me for a repeat NCS which showed the same findings.

At this time I related to my neurologist that I had noticed, particularly in the past year, unsteadiness in my gait. She related that the vibratory sense in my feet was reduced, and this, along with the numbness, was the likely cause of this new symptom; simply stated, I couldn’t tell where my feet were without looking.

I had laboratory studies which were unremarkable except for two findings; I had very elevated immunoglobulins, IgG and IgM, both being more than a thousand above normal limits. I was told that this signified that I had a Gammopathy. The incidence is 1% of the population over age 50 and 3% over the age of 70. The majority of these are termed macroglobhulinemia, unspecified, or MGUS, and in most instances this is benign. However 10% develop a peripheral neuropathy which is where I fall. What happens is that the anti-MAG (Myelin Associated Glycoprotein) antibodies in the IgM attach to the myelin sheath of the nerves and destroy it. I am not sure what destroys the axon, perhaps the antibody in the IgG. They can measure the anti-MAG antibody, itself, and my level was high as you would expect.

After I had digested all this information, the next logical question to ask was what about treatment? Initially I was told by my two neurologists that, inasmuch as my disease had been progressing slowly, I might be better off not having treatment as I would probably die before it got bad enough to really bother me. Ha, Ha (a little gallows humor)! But what bothers me most is having an unsteady gait and the fear of falling, such as on going up and down stairs, especially if there is no railing.

My hematologist, who had done the lab studies, called me to come in to discuss my situation. He had talked to my neurologists (the docs at OHSU are really good and caring). He recommended that I consider a new treatment that was just getting underway around the country; however, there were yet no completed studies but the results coming in were promising. Rituxan is a monoclonal antibody that is being used in the treatment of breast and colon cancer. It reduces the antibodies produced by the plasma cells in the bone marrow, including IgG and IgM which should then reduce their attack on the nerve cells. The effect is not permanent but so far it has been shown to last at least a year in most cases. If IgG and IgM go up in the future, I can have another series of treatments.

So, this Wednesday I go in for my first infusion of Rituxan which will take 5 – 6 hours I am told. I will then have 3 more infusions a week apart but these will be faster, taking only 2-3 hours. I told Patti to bring a book along to keep me company and I think I will bring a Sudoku with me

The Rituxan is not like the chemotherapies they use for cancer treatment. It has some side effects but not like the former. Incidentally, the cost of the treatment is $20,000. Thank goodness for Medicare.