# Monoclonal Gammopathy: Is the Protein Injuring the Kidney?

Establish the renal lesion and its relationship to the clone before choosing treatment.

![Infographic: Monoclonal Gammopathy: Is the Protein Injuring the Kidney?](https://urinenephrology.org/visual-reference/images/student-monoclonal-kidney.png?v=20261003c)

## A small clone can matter

A low M-spike does not exclude kidney injury. MGRS links a nephrotoxic monoclonal immunoglobulin to a renal lesion when the clone does not otherwise meet hematologic treatment criteria.

## Recognize the pattern

Look for unexplained proteinuria, hematuria, AKI, declining filtration, or proximal tubular dysfunction. A urine dipstick can miss light-chain protein; compare albumin with total urinary protein.

## Use complementary tests

Combine serum and urine electrophoresis, immunofixation, and free light chains. Kidney function and assay context affect interpretation. A monoclonal blood result alone does not prove renal causality.

## Pathology connects the diagnosis

Biopsy assessment may require light microscopy, immunofluorescence, electron microscopy, and deposit typing. Distinguish amyloid, nonamyloid deposits, glomerular inflammation, proximal tubulopathy, and casts.

## Coordinate treatment

Nephrology, hematology, and pathology identify the lesion and clone. Treatment depends on both. Suspected myeloma-related AKI requires prompt evaluation; fluids and dialysis decisions follow the clinical context.

## Avoid the shortcut

Monoclonal protein plus cardiac imaging does not establish AL amyloidosis. Confirm and type amyloid when suspected. Track hematologic response and kidney response separately; one does not guarantee the other.

## Supporting evidence

- [PubMed 30510265](https://pubmed.ncbi.nlm.nih.gov/30510265/)
- [PubMed 25607108](https://pubmed.ncbi.nlm.nih.gov/25607108/)
- [PubMed 31409583](https://pubmed.ncbi.nlm.nih.gov/31409583/)
- [PubMed 37414019](https://pubmed.ncbi.nlm.nih.gov/37414019/)

## Source lessons

- [monoclonal gammopathy kidney student handout](https://urinenephrology.org/student-resources/advanced/monoclonal-gammopathy-kidney-student-handout.html)

Read alongside the full lessons; the findings and decisions shown here require the stated clinical context.