Which of the following is not an autoimmune disease?

Psoriasis, Vitiligo and Rheumatoid arthritis are autoimmune diseases. An illness that occurs when the body tissues are attacked by its own immune system is known as autoimmune disease. Alzheimer's is caused by brain cell death. It is a neurodegenerative disease. There is progressive brain cell death that happens over time. Thus the correct answer is Alzheimer's disease.