Autoimmune Diseases

Autoimmune diseases are a category of illness, involving many different mechanisms and causes. The medicines we use to treat them work by interacting with your immune system in a few ways

  • Some deactivate the system as a rescue measure (eg: corticosteroids),
  • Some insulate parts of your body from itself (eg: mesalamine, which lines the bowel to protect against ulcerative colitis).
  • Others attempt to affect specific response mechanisms:
    • by desensitization (eg: Flonase, a nasal steroid),
    • or by blunting the response (T-cell and B-cell suppressors).

My favorite nugget about the immune system is that there exist “natural killer cells”. This is how your body defends against the innumerable cancerous cells that will develop during your conversion from a single cell to a being. UpToDate’s “overview of autoimmunity” is a good introduction the pathophysiology of autoimmunity. Unfortunately, there is no equivalent easy-to-digest single article regarding immunotherapeutics. Also, a new category of drugs in the last 20 years, with new drugs coming out every year, attempt to deactivate or otherwise interact with the pathogen itself and “deactivate it”. That’s how we treat rabies, for example, although rabies is a more crude, shotgun drug, unlike the very targeted immunotherapies for things like cancer nowadays.

A good case by which to understand autoimmune therapy is treatment for Ulcerative Colitis and Crohn’s disease. When someone presents in a severe flare:

  • You control it in the immediate phase with salvage therapy that severely ramps down the immune system (corticosteroids like prednisone or if that doesn’t work then IV methylprednisolone)
  • Then, you try to control it by giving mesalamine, a form of aspirin that lines the colon and basically works as a local NSAID to reduce the inflammation response itself.
  • If that doesn’t work, then you try biologic agents like remicade which is an antibody you get every 3 months or so that deactivates all the TNF-alpha in your body to shut down a particular inflammatory pathway.
  • If that doesn’t work, you call a general surgeon, and they take out either part of or your entire colon.

For an anatomically confined variant like ulcerative colitis which as its named only affects the colon (vs crohn’s which can happen anywhere in the enteric tract from mouth to anus), you can do it in a controlled fashion and take out the entire colon even if the inflammation hasn’t reached all the way through it yet, and then use sphincter-sparing techniques and use the end of the small bowel to create a neo-rectum so the person isn’t shitting in a bag for the rest of their life.

This was ghostwritten by my good friend Abhishek MD

Written on December 21, 2019