Fibromyalgia Syndrome (FMS) is a non - inflammatory condition characterized by the presence of chronic, widespread musculoskeletal pain and tenderness; FMS is considered to be the result of increased processing of pain by the central nervous system.

Axial spondyloarthropathy is the hallmark of Ankylosing Spondylitis (AS), an inflammatory joint disease involving the axial spine, the sacroiliac joints as well as peripheral joints.

Although FMS and AS differ vastly in their pathogenesis, a considerable clinical overlap may exist between these conditions. Both disorders typically cause chronic nocturnal back pain and disturbed sleep may accompany either condition. In addition,the investigators have previously described an increased prevalence of (secondary) FMS among female AS patients.

This overlap may have important clinical implications since the presence of comorbid FMS may lead to increased severity results on commonly used instruments in the evaluation of disease activity in AS, such as the BASDAI and BASFI .

Recently, the Assessment of Spondyloarthritis international Society (ASAS) has published updated classification criteria for axial spondyloarthropathy. These criteria, which are summarized in table 1, are based on the evaluation of patients suffering from chronic back pain with an age of onset of less than 45.

Objective:

The objective of the current study is to evaluate the prevalence of axial spondyloarthropathies among FMS patients, utilizing the new ASAS criteria.

Inclusion Criteria:

Patients fulfilling American College of Rheumatology criteria for classification of Fibromyalgia:

• Widespread pain lasting over three months
• Tenderness in at least 11 of 18 points

Exclusion Criteria:

• Patients with known inflammatory joint disease prior to the study
• Patient not able to give informed consent
• Pregnant women

Patients will be recruited consecutively from the Fibromyalgia clinic as well as the general rheumatological clinic of the Tel Aviv Sourasky medical center.