Chronic arthritis in two children with partial deletion of chromosome 18.

We describe 2 children with a partial deletion of chromosome 18 and chronic arthritis. A boy with r(18)(p11.3; q23) lacked serum IgA and had arthritis affecting both knees. A girl with del (18)(q21.2; q22) had arthritis in 5 joints. Her serum IgA was normal. In both children, the arthritis responded to nonsteroidal antiinflammatory drugs.