Over three weeks ago, after having issues with my methotrexate, my rheumatologist switched me to another immunosuppressant, azathioprine.

This drug best work without major side effects. That it starts with the letters A and Z is fitting because after azathioprine, for a largely amyopathic form of dermatomyositis, like mine, my doctors and I are out of realistic options.

Like methotrexate, scientists first developed and used azathioprine for chemotherapy. Scientists later discovered its use in suppressing the body’s formation of antibodies—proteins used by the immune system to neutralize anything that can produce disease. During the 1960s and 1970s, it became widely used for kidney and heart transplants, then later for rheumatoid arthritis.

Azathioprine works by inhibiting purine synthesis, a process in which the body produces organic compounds essential to synthesizing white blood cells. Since some of my white blood cells are attacking my skin (and to a lesser extent, my muscles), inhibiting their proliferation keeps a malfunctioning, overactive immune system like mine in check.

Interestingly, caffeine and theobromine (found in chocolate) are purines. The body specifically relies on purine synthesis to process both. That may explain my heart palpitations after one-too-many cups of coffee.

Azathioprine is finally healing my rashes

After only three weeks, my skin looks better than it has in a months, possibly since last June. The rashes have reduced and stopped itching altogether.

My scalp still itches and flakes in a manner that at times, is almost painful. My hair is also still slowly falling out. To date, the only drug to control these symptoms is prednisone in moderate doses.

I even feel stronger than I did on methotrexate and seem to build muscle more quickly.

As I wrote last week, I now need to control the chest tightness and shortness of breath. As I work up to the full dose, I think these symptoms will also go away.