ASH 2025 | Diagnosing MGRS: the central role of kidney biopsy

So MGRS or monoclonal gammopathy of renal significance needs to be considered in anybody who has a monoclonal gammopathy and has proteinuria or renal dysfunction by virtue of having an elevated creatinine or new onset hypertension or microscopic hematuria in the setting of a monoclonal gammopathy. And really, the most important thing is, number one, to, in almost all cases, have those patients have a kidney biopsy because the kidney biopsy is essential to define the pathologic entity, which is what really defines MGRS. And then also have an evaluation for the monoclonal gammopathy in case you establish a diagnosis of MGRS, you want to know what the clone is either circulating or in the bone marrow because the treatment of the disease is targeted towards the particular clone. Unfortunately, sometimes in about 30% of patients with a particular diagnosis of PGN-MGRD or proliferative glomerulonephritis with monoclonal gammopathy, you cannot find the clone or the immunoglobulin, only the pathologic findings in the kidney biopsy. But we do know if we target the clonal disease, we can often halt the continuous kidney deterioration that happens in the absence of treatment. In terms of working patients up, I think it’s really essential for hematologists to understand that a 24-hour urine collection which is sent for both urine protein electrophoresis and immunofixation and urine total protein is really essential because that’s what defines the amount of monoclonal gammopathy that’s in the urine and that can very much distinguish patients with myeloma-related kidney dysfunction such as cast nephropathy versus patients with an MGRS that has more albuminuria and less of a urine M-spike.

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