IgA Nephropathy and Atypical Anti-GBM Disease: A Rare Dual Pathology in a Pediatric Rapidly Progressive Glomerulonephritis.

Introduction: Anti-GBM nephritis in the pediatric age group is exceedingly rare with concurrent additional pathologies being even rarer. Tissue diagnosis requires a combination of crescentic histomorphology, immunofluorescence showing "paint brush stroke" pattern of linear IgG or rarely IgA, and serum anti-GBM antibodies subject to the disease course and treatment. The authors describe one such case with a dual pathology involving IgA nephropathy and atypical anti-GBM disease. Case Presentation: A 13-year-old girl presenting with features of rapidly progressive glomerulonephritis underwent a renal biopsy showing a mesangioproliferative histology with crescents and an immunofluorescence pattern indicating a dual pathology of IgA nephropathy and anti-GBM nephritis. Additional ancillary testing including staining for IgG subclasses and galactose-deficient IgA (KM55) helped to confirm the diagnosis. She responded to steroid pulses and plasma exchange therapy, was off dialysis after 8 weeks with a serum creatinine level of 1.5 mg/dL, and however remains proteinuric at last follow-up. Conclusion: Concurrent anti-GBM nephritis and IgA nephropathy is a rare occurrence and possibly arises from a complex interaction between the anti-GBM antibodies and the basement membrane unmasking the antigens for IgA antibodies. Additional newer techniques like immunofluorescence for KM55 are helpful in establishing the dual pathology.