A man dies of renal failure and his urinalysis shows the presence of Bence Jones protein. What is the most likely diagnosis?

The presence of Bence Jones protein in the urine is a key indicator in diagnosing multiple myeloma, a type of plasma cell dyscrasia characterized by the abnormal proliferation of monoclonal plasma cells. These cells produce excess immunoglobulin light chains, which can be filtered through the kidneys and subsequently appear in the urine as Bence Jones proteins.

In this scenario, the man’s renal failure coupled with the identification of Bence Jones protein strongly suggests that his renal impairment is due to the consequences of multiple myeloma, potentially leading to renal damage through mechanisms such as cast nephropathy or light chain deposition disease.

While acute tubular necrosis can lead to renal failure, it is typically associated with different findings in urinalysis. Similarly, lipoid nephrosis and membranous glomerulonephritis have distinct clinical and laboratory features that do not typically include the presence of Bence Jones protein. Amyloidosis can also occur in the context of multiple myeloma, as the excess light chains may misfold and deposit as amyloid; however, the direct relationship of Bence Jones protein primarily points towards a diagnosis of multiple myeloma itself, highlighting its significance in this clinical context.