Your immune system creates inflammation to combat injury or disease. But if you have an inflammatory disease such as polymyalgia rheumatica (PMR), your immune system may go from defender to attacker. Although the exact cause of PMR is uncertain, the disease involves inflammatory cells that produce pain and stiffness primarily in the shoulder and hip areas. Its not life threatening, and unlike inflammatory conditions such as rheumatoid arthritis, PMR does not erode your joints. However, it can affect your quality of life, and it increases your risk of another, potentially serious medical condition. PMR is not thought to be a destructive joint process, says Matthew Bunyard, MD, director of Clinic Operations with Cleveland Clinics Department of Rheumatic and Immunologic Diseases. But, symptoms are symptoms, and for most people the disease gives them enough trouble that theyll go to the doctor to find out whats going on.