Occurrence of fibromyalgia in patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease that affects the axial skeletal system, causing pain and functional incapacity. To measure the impact of AS on patient's life, questionnaires are used to assess disease activity (BASDAI); functional incapacity (BASFI); and quality of life (ASQoL). Fibromyalgia (FM) is one of the most common causes of generalized pain and can coexist with other diseases; it can be assessed by the Fibromyalgia Impact Questionnaire (FIQ). Few studies have demonstrated correlations between FM and AS. The present study obtained data regarding the epidemiologic profile of patients with AS and FM and evaluated the prevalence of FM in patients with AS. The FM influence on BASDAI, BASFI and ASQoL test scores was assessed.

A total of 71 patients with AS, diagnosed according to the modified New York criteria, were studied. Clinical and functional assessment was performed and BASDAI, BASFI and ASQoL tests were applied. Patients with a diagnosis of FM were evaluated through the FIQ.

Eleven patients met the criteria for FM; thus a FM prevalence of 15% was observed among the patients with AS. FM was more prevalent among women (3.8:1). Age at disease onset (AS) was 27.5 years. The HLA-B27 antigen was positive in most of them (80.4%). When comparing BASDAI, BASFI and ASQoL test means, it was observed that values are significantly higher (P < 0.01) among patients with FM. We concluded that the coexistence of FM can worsen AS activity aspects, as well as functional incapacity and quality of life.