Rare Case of Dense Deposition Disease with Combined C3 and C4d Deposits with MYH9-related Mutation

Abstract

Background: The C3 glomerulopathies are a group of rare forms of glomerulonephritis with an incidence of 1-2 cases per million. It is mainly characterized by dysregulation of the alternative complement pathway. It is further classified morphologically based on electron microscopy ultrastructural findings into Dense Deposition Disease (DDD) and C3 glomerulonephritis. DDD is normally characterised by C3 Deposits. Case: We report a rare case of a young Emirati male who presented with sub nephrotic proteinuria and microscopic haematuria on routine evaluation. Renal biopsy showed features of DDD with combined C3 and C4 deposits. The retinal evaluation showed features of Drusen classically seen in DDD. Genomic study showed heterozygous mutation in c.5842G>C (p.Asp1948His) variant of uncertain significance in MYH9 gene. Discussion: C3 Glomerulopathy is a type of immune mediated disease previously classified as membranoproliferative glomerulonephritis. DDD is mainly characterised by C3 deposits in the glomerular basement Membrane. Our case has both C3 and C4d deposits, which is a rare entity. It shows the activation of both classical and alternate pathways. Conclusion: Dense deposition disease is a rare complement mediated glomerulopathy. It is characterised by C3 deposits. Dense deposition disease with combined C3 and C4d deposits is a new entity. The treatment and prognosis of such cases will be different and unique compared to the normal cases of DDD.