Diagnosis of "rheumatoid variants" ankylosing spondylitis, the arthritides of gastrointestinal diseases and psoriasis, and Reiter's syndrome.

Four rheumatic diseases-ankylosing spondylitis, the arthritis accompanying ulcerative colitis or regional enteritis, psoriatic arthropathy, and Reiter's syndrome-formerly considered to be forms of rheumatoid arthritis, are now distinguished from that disorder and should be recognized by the physician as entities. These arthritides may be distinguished from each other by a number of clinical and radiographic characteristics, principally (1) the roentgenographic appearance of the spine when spondylitis is present, (2) the location of periosteal new bone formation, (3) the location of arthritis in the joints of the limbs, and (4) the presence of characteristic skin lesions.