Cystic rheumatoid arthritis with Felty's syndrome and ankylosing spondylitis.

A 63-year-old man with strictly axial ankylosing spondylitis since the age of 28 years had a seven-year history of cystic seronegative rheumatoid arthritis with Felty's syndrome. Cysts were present in the hands, feet, wrists, shoulders, hips, one elbow, and one knee. There was no evidence of juxtaarticular demineralization, joint space loss, erosions, or joint destruction. Rheumatoid pannus was demonstrated within the cysts, particularly at the hip, ruling out cystic hip disease due to ankylosing spondylitis. HLA typing demonstrated the B27 and DR4 haplotypes. HLA B27 may be associated with a worse prognosis of rheumatoid hip involvement.