Shedding light on fundus drusen associated with membranoproliferative glomerulonephritis: Breaking stereotypes of types I, II, and III

Purpose: Membranoproliferative glomerulonephritis (MPGN) classification has been changed from purely anatomic to molecular. This report describes two cases of MPGN with associated drusen that exemplify the importance of this change and the need for ophthalmologists to understand it. Methods: The medical and pathologic records of two patients with MPGN and drusen were examined. Results: Two patients with MPGN and risk-associated alleles of complement factor H were found to have drusen. In one case, the process led to severe visual impairment. Based on anatomic classification, one patient had MPGN Type I and the other had MPGN Type III. However, both patients had renal biopsy findings classic for C3 glomerulonephritis and the same genetic abnormality (risk-associated alleles of complement factor H). Conclusion: The association of MPGN and drusen needs to be reevaluated. Previously only recognized in association with Type II MPGN, drusen have been demonstrated in 2 patients with C3 glomerulonephritis in this report. These drusen are likely the result of complement pathway abnormalities. The authors propose a new nomenclature in the ophthalmic literature to classify pathology as immune complex-mediated or complement-mediated rather than solely by the electron microscopy findings. This nomenclature will better characterize the underlying genetic abnormalities and pathophysiology of these disease processes.