Pathogenesis of seronegative arthritis.

The concept of seronegative spondarthritis, linking several diseases around ankylosing spondylitis, has received considerable clinical and genetic support, especially through the discovery of a high frequency of HLA-B27 in these disorders. Exogenous factors would appear to be responsible for some manifestations of the disease, but the role of Klebsiella micro-organisms is equivocal, and dietary control does not affect clinical manifestations. Increased serum and salivary IgA antibodies in active ankylosing spondylitis patients tend to suggest that IgA may act as an acute-phase reactant.