Reactivity of serum antibodies to the keratin layer of rat esophagus in patients with rheumatoid arthritis.

Serum antibodies reactive with the keratin layer of rat esophagus (AKA) were found in 46 of 80 (57.5%) rheumatoid arthritis (RA) patients. In contrast, AKA were present in only 7 of 82 (9.