Chronic Lymphocytic Leukaemia (CLL)-Associated Proliferative Glomerulonephritis With Monoclonal Immunoglobulin Deposits (PGNMID) Diagnosed in the Absence of Detectable Paraprotein.

Renal involvement in chronic lymphocytic leukaemia (CLL) is uncommon but clinically relevant. We report a man in his early 70s with known CLL who presented with non-nephrotic proteinuria, progressive kidney injury, and hyperkalaemia. Kidney biopsy revealed diffuse membranoproliferative glomerulonephritis with IgG kappa monoclonal deposits on immunofluorescence and electron microscopy, establishing a diagnosis of CLL-associated proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID). Treatment with rituximab and chlorambucil resulted in significant improvement of both kidney function and proteinuria. This case highlights the pivotal role of kidney biopsy in CLL-associated nephropathy: it established a precise diagnosis in the absence of detectable circulating paraprotein, triggered clone-directed therapy, and demonstrated that meaningful renal recovery is achievable even in the context of acute kidney injury.