Rheumatology is a sub-specialty in internal medicine, devoted to diagnosis and therapy of rheumatic diseases. Physicians who specialize in rheumatology are called rheumatologists. Rheumatologists deal mainly with clinical problems involving joints, soft tissues, autoimmune diseases, vasculitis, and heritable connective tissue disorders. Many of these diseases are now known to be disorders of the immune system. Rheumatology is increasingly the study of immunology.