Thank you, John, for presenting a case of a middle-aged woman with significant weight loss and chronic diarrhea.
- Initial approach to diarrhea often involves determining first duration of symptoms (acute vs. chronic) and then assessing whether the quality of the diarrhea (inflammatory vs. non-inflammatory). Inflammatory diarrhea, in addition to being accompanied by systemic symptoms, may be bloody and include elevated stool calprotectin, stool WBCs, or stool lactoferrin.
- Consider multiple myeloma when you start to see evidence of the CRAB criteria – Calcium elevation, Renal injury, Anemia, and Boney pain.
- The overlap between MM and chronic diarrhea can be through amyloid! Up to 10% of patients with MM may have amyloidosis as a secondary complication. Patients with amyloidosis who have MM have a worse prognosis than those who do not.
Break down of diarrhea based on duration of symptoms and inflammatory vs. non-inflammatory causes (courtesy of prior blog post from Rabih that’s full of diarrhea info!)
Multiple Myeloma and Amyloid
- HH Pearl: Up to 10% of patients with MM may have AL amyloidosis as a secondary complication. The two conditions are often diagnosed around the same time. Occasionally though, the development of full-on MM can lag behind the clinical diagnosis of amyloid by 6 months!
- Amyloid can occur in other plasma cell dyscrasias as well, such as Waldenström macroglobulinemia.
- Patients with amyloidosis who have MM have a worse prognosis than those who do not.
- In a retrospective analysis of 147 patients with biopsy-proven AL amyloidosis who also had specialized testing for determination of circulating plasma cells, 20 patients had concurrent MM.
- Patients with both AL amyloidosis and MM had a significantly worse prognosis than those with AL amyloidosis alone (14 versus 32 months).
How does myeloma affect the kidney? There is a huge list but here are the main mechanisms (from prior Kevin Duan blogpost!)
- Myeloma cast nephropathy: all those proteins collect as casts and can cause tubular injury (remember that Tamm-Horsfall thing?)
- Amyloidosis: increased AL amyloid production takes place in mesangial cells causing damage to the glomerulus
- Immunoglobulin deposition disease: similar mechanism of damage to amyloid, where immunoglobulin deposits in the glomerulus