Karrnan Pathmanandavel¹, Adrian Lee¹, Maria Dela Cruz¹, Suzanne Culican¹, David Campbell¹, Mark Acebes¹, Jonathan Emerson¹, Lawrence Ong¹, David Brown¹, Sarah Sasson¹, Ming Wei Lin¹, Lucinda Berglund¹

¹Department of Immunology and Immunopathology, ICPMR, Westmead Hospital, Sydney, Australia

Proliferative Glomerulonephritis with Monoclonal Immune Deposits (PGNMID) is a renal disease characterised by monoclonal deposition of immunoglobulins, often IgG3 subclass restricted, in the glomerulus. This entity is heterogeneous in its presenting features, demographics, and clinical outcome – with occasional cases of spontaneous remission but 20% progressing to end-stage kidney disease. Interestingly, only a minority (~ 30%) of patients have detectable circulating paraprotein or a clonal population on flow cytometry. Thus, the pathogenesis of PGNMID is unclear, complicating the choice of B-lineage depleting therapy (e.g., rituximab vs. bortezomib). 

We have identified a surprisingly high frequency of PGNMID cases where the light chain clonality observed on renal direct immunofluorescence is opposite to that seen on other studies. This highlights the need for a holistic approach to diagnosis with correlation between multiple test modalities, and particularly the value added by IgG subclass staining. These cases have also suggested novel research approaches to better understand the pathogenesis of this enigmatic entity.