Answer: An autoimmune disorder.
Explanation:
Autoimmune disease are diseases by which one's own immune system mistakenly attacks healthy cells in the body.
Normally the immune system guards the body against germs like bacteria and viruses when it senses these foreign invasion, but in autoimmune disorders, the immune system abnormally attacks and destroys healthy tissues in the body by mistakenly identifying them as foreign.
Some examples of autoimmune disorders are; Rheumatoid arthritis, Lupus, Multiple sclerosis (MS), Inflammatory bowel disease (IBD). Etc.
