Pseudothrombocytopenia and IgA-related platelet agglutinin in a patient with IgA nephritis.

A 41-year-old female was evaluated for asymptomatic proteinuria and thrombocytopenia. The renal biopsy disclosed mild to moderate mesangial proliferation, and the immunohistology showed granular deposition of dominant IgA and C3 in the mesangium, which is consistent with IgA nephritis. Thrombocytopenia was EDTA-dependent pseudothrombocytopenia type 1. Heparinized blood restored the platelet count to normal. Serological examinations revealed that the platelet agglutinin was IgA, and the platelet clumping required both EDTA and IgA-related agglutinin. Thus, the present case adds the combination of IgA nephritis and pseudothrombocytopenia to the spectrum of the so-called thromborenal syndrome. In view of recent findings that platelet agglutinins belong to immunoglobulins or fractions, occurring frequently in a variety of immunologically abnormal situations, IgA-related agglutinin as seen in this patient may have more than a chance association with IgA nephritis.