RESUMO
Benign Joint Hypermobility Syndrome (BJHS) is characterized by generalized ligamentous laxity, with associated tendency to recurrent sprain and dislocation. Whereas ankylosing spondylitis (AS) is characterized by ankylosis and loss of mobility of the affected joints by fibrosis and ossification of cartilage and enthesis. The association of these two pathologies is rare. We report on a 18-year old man with a joint hypermobility and laxity as well as accompanying 18-month history of back pain at the lumbar spine, both knee and left buttock pain. At physical examination the patient presented 5 points of Nine-Point Beighton hypermobility score and limitation of movement in the lumbar spine due to back pain. Magnetic resonance imaging of the pelvis showed bilateral sacroiliitis and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were elevated and HLA B27 was positive. Transthoracic echocardiography and opthalmologic examination excluded other cause of joint hypermobility. We diagnosed co-existent BJHS and AS.