Heavy Chain Deposition Disease in Monoclonal Gammopathy of Renal Significance: A Prodrome of Multiple Myeloma Case and Literature Review.

Monoclonal immunoglobulin deposition disease (MIDD) is a complication of plasma cell dyscrasias, resulting in abnormal immunoglobulin deposition along basement membranes. We describe a case of a 60-year-old male with a complex hospital admission, presenting with critical illness accompanied by acute kidney injury, nephrotic syndrome and moderately elevated serum free light chain (SFLC) ratio, on a background of well-controlled diabetes, hypertension and chronic kidney disease. There was no clear aetiology for his presentation following preliminary examination and investigations, which led to a biopsy diagnosis of heavy chain deposition disease (HCDD) in the context of monoclonal gammopathy of renal significance (MGRS). We explore the importance of understanding the disease course to allow timely biopsy diagnosis and treatment initiation. Our patient required very close follow-up and a wide multi-disciplinary approach, including haematologists, nephrologists and histopathologists, to guide management in a disease for which therapeutic strategies are poorly defined due to limited clinical trial data.