Relation of microscopic haematuria in ankylosing spondylitis to circulating IgA containing immune complexes

Ankylosing spondylitis (AS) is associated with IgA nephropathy. To study the pathogenetic mechanism of this association the presence of haematuria and circulating IgA containing immune complexes (IgA ICs) in 70 patients with AS was determined. In this retrospective study haematuria was present in 15 patients and 25 patients had IgA ICs. Circulating IgA ICs were shown in 9/15 (60%) of the patients with haematuria and in 16/55 (29%) of those without haematuria. These results suggest that IgA ICs in patients with ankylosing spondylitis have a pathogenetic role in causing IgA nephropathy.