Case report: mesangial IgA-IgG deposition in mixed cryoglobulinemia.

Glomerular deposits of immunoglobulin A (IgA) (and immunoglobulin G [IgG]) has been described in IgA-nephropathy (Berger's disease), in anaphylactoid purpura, and systemic lupus erythematosus. The pathogenesis of mesangial IgA deposits in these disease states is unclear. Circulating immune complexes have been speculated to be involved although their existence in blood in IgA nephropathies have never been reported. We describe a 53-year-old man who presented with a petechial rash in lower extremities accompanied by painful swelling of left ankle and wrist. Polyclonal elevation of IgA and IgG in serum was found, along with cryoglobulins containing IgA and IgG (rheumatoid factor positive). After two years, hematuria, mild proteinuria, and active urinary sediment developed and renal biopsy revealed focal proliferative changes. Immunofluorescence revealed predominantly mesangial deposits of IgA and IgG but no IgM nor complement. This experience suggests that circulating complexes consisting of IgA and IgG may lead to renal lesions presenting clinically and histologically in a way similar to that commonly seen in IgA nephropathies.