Ankylosing spondylitis is part of a multifactorial syndrome: hereditary multifocal relapsing inflammation (HEMRI).

Complex associations between the different subgroups of seronegative arthritis, acute anterior uveitis, psoriasis and inflammatory bowel disease were found in a series of patients and relatives. Different HLA-B antigens were associated with different clinical signs. The results indicated the existence of a multigenic syndrome whose main clinical manifestations are relapsing innflammations at various sites. The genetic factors appeared to be 1) HLA-B27 associated disease susceptibility, 2) predisposition to psoriatic arthropathy, 3) predisposition to early onset familial psoriasis and, 4) a probable predisposition to inflammatory bowel disease and its associated arthropathy. The results indicated that the different genetic factors may interact and influence each other's penetrance and expression.