Hi, Neither fibromyalgia nor spondylitis is other names for arthritis. Let me explain more: -Spondylitis is a usual term for inflammation of the spine (vertebral bones of the neck, thorax, lumbar and sacral). Usually spondylitis is used instead of the complete name Ankylosing Spondylitis . Ankylosing Spondylitis (AS) is a rheumatologic disorder that induces inflammation and stiffness in the vertebra and the soft tissues around them (sometimes also other joints). - Fibromyalgia (FM) is not considered as a true rheumatologic disorder and it does not induce inflammation. The problem in fibromyalgia is decreasing the threshold for pain perception in all the body. In that case, the patients feels pain in multiple areas of the body and he/she feels pain even by a light pressure (that other people don t consider it as painful). AS and FM are two distinct problems and both are seen more in females than males. Although it is possible that someone has both AS and FM, but in most situations, this is not the case. The diagnosis of AS is by blood tests, vertebral x-ray, history and physical exam, and the diagnosis of FM is mainly by history and physical exam. So, recommend that you refer to a rheumatologist or Physical Medicine and Rehabilitation specialist (Physiatrist) at your area to have a more accurate diagnosis for you. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Hooman Mahmoudi, Neurologist