A 41-year-old-white man with achondroplasia has been followed intermittently since age 27. During this time, he has complained of neck and back pain with limited mobility in both. Other problems have included temporomandibular joint pain, dysuria without apparent urinary tract infection iritis, anemia, and an elevated gamma globulin fraction. Recently he returned to the clinic complaining of rigidity of the entire spine. Radiographs showed complete fusion of the sacroiliac joints and fusion of the cervical vertebral bodies and apophyseal joints, consistent with ankylosing spondylitis. He was found to be HLA B-27 positive. This case illustrates the importance of considering other diseases whenever atypical orthopedic problems arise in patients with a bone dysplasia.