[Possible diagnostic error of "Bechterew disease"].

A 41-year old caucasian male presented with limited range of motion of the entire spine and myogenous intermittent claudication. He was referred with the diagnosis "ankylosing spondylitis". The clinical picture mimicked ankylosing spondylitis, but there were no corresponding radiological abnormalities despite a 13-year history of his disease. Laboratory values showed markedly elevated levels of muscle enzymes. The diagnosis of rigid spine syndrome, a subtype of muscular dystrophy, was made from the clinical picture a normal EMG and degenerative changes on a biopsy from the muscle trapezius. We would like to draw attention to this rare cause of back pain.