Supplementary Material for: An unusual presentation of MPO-associated glomerulonephritis and suspected IgA mediated anti-GBM disease: a case report

Introduction: Anti-glomerular basement membrane (GBM) disease is a rare cause of glomerulonephritis usually mediated by IgG antibodies and is associated with ANCA-associated glomerulonephritis in up to 50% of cases. IgA mediated anti-GBM disease is extremely rare and presents diagnostic difficulties as circulating IgA antibodies will not be detected by standard serological tests for anti-GBM disease. Case presentation: We present the case of a 67 year old man with rapidly progressive glomerulonephritis requiring haemodialysis at presentation. Serological testing was positive for anti-MPO and negative for IgG anti-GBM antibodies. Kidney biopsy revealed necrotizing crescentic glomerulonephritis with linear staining of IgA along the GBM. He was treated with a combination of immunosuppression and plasma exchange and was able to become dialysis independent. Conclusion: To our knowledge, this is the first documented “double positive” IgA anti-GBM disease and ANCA-associated glomerulonephritis.