Coexistence of hereditary multiple exostoses and ankylosing spondylitis

We report a 50-year-old male patient with hereditary multiple exostoses (HME) and ankylosing spondylitis (AS). This is the first case reporting the coexistence of HME and AS. Our patient has multiple exostoses around the knee, elbow and wrist joints. At the age of 40 years, pain in the lower back associated with morning stiffness lasting about an hour and improving with exercise began. His son also has hereditary multiple exostoses but has no sign of AS. HME is an autosomal dominant disorder. AS has a remarkably strong association with the histocompatibility antigen HLA-B27. Owing to the different genetic mechanisms, it is not possible to differentiate between coincidence and association. Coexistence of HME and AS in our patient probably represents a coincidence rather than a real association.