We read with interest the article by Heras et al.1 They reported the occurrence of IgA nephropathy (IgAN) in two sisters, one of whom had lupus anticoagulant (LA) and wondered whether this association was incidental or related to a common immune pathogenetic mechanism.1
Although not extensively studied in IgAN, there have been some reports on the associations of antiphospholipid antibodies with Henoch-Schönlein purpura (HSP),2, 3 which has a common pathogenesis of IgAN. Also, Kawakami et al.4 recently reported a relatively high prevalence of antiphospholipid antibodies in adults with HSP. In their report, 4 22 (73%) of the 30 HSP patients were positive for serum IgA anticardiolipin antibodies, 19 (63%) had IgA anti-phosphatidylserine-prothrombin complex (anti-PS/PT) antibodies and 20 (67%) IgM anti-PS/PT antibodies, suggesting that the prevalence of antiphospholipid antibodies have been underestimated in patients with HSP in the past, although thrombotic episodes were not evident in their patients.4 They also showed that serum IgA anticardiolipin antibody levels were also significantly associated with proteinuria (a marker of nephritis severity).4 Considering the similarity of renal histopathology between IgAN and HSP nephritis, antiphospholipid antibodies may have a pathogenic role in the development of IgA-mediated glomerulonephritis.
Furthermore, because some authors showed that antiphospholipid antibodies could cause thrombosis in patients with HSP,2, 3 and it was reported that anticardiolipin antibodies of IgG, IgM and IgA isotypes from patients with the antiphospholipid syndrome could play a role in thrombosis in vivo,5 careful clinical monitoring for thrombosis would be necessary in patients with HSP or IgAN who show positive antiphospholipid antibodies.
Therefore, further studies should be performed to evaluate the prevalence and pathogenic role of antiphospholipid antibodies in patients with IgAN and the relationships among antiphospholipid antibodies, the severity of IgAN, and thrombosis should be further elucidated in the future.
