M36: Systemic disorders of connective tissue in diseases classified elsewhere

M36.4: Arthropathy in hypersensitivity reactions classified elsewhere

The immune system protects the body from pathogens and foreign substances. The immune system can also destroy cells in the body that have pathologically changed. Some of the immune system’s antibodies can make pathogens and foreign substances visible to the immune system. Other antibodies attack pathogens or foreign substances directly.

When it overreacts, the immune system can produce antibodies that target the body’s own tissue, for example. When the antibodies attack the joints, the joints can get damaged. This can cause joint problems.