Rheumatologists specialize in and provide treatment for various autoimmune diseases that affect the joints, muscles, and blood vessels. Some conditions for which patients seek care from a rheumatologist include rheumatoid arthritis, ankylosing spondylitis, gout, polymyalgia rheumatica, and systemic autoimmune diseases, such as lupus, myositis, systemic sclerosis, uveitis, and vasculitis.