Late-stage myeloma invades kidney without significant effect on renal function: findings from 53 autopsies in a...

Area of Science:

• Nephrology
• Oncology
• Pathology

Background:

• Renal manifestations like cast nephropathy, amyloidosis, and calcification are known in multiple myeloma (MM).
• The severity of histopathological findings and their clinical significance in MM-related kidney disease remain unclear.

Purpose of the Study:

• To investigate the relationship between the severity of renal histopathological findings and clinical characteristics in patients with MM.
• To clarify the clinical significance of various renal pathologies in MM.

Main Methods:

• Analysis of kidney tissues from 53 autopsies of patients who died from MM.
• Evaluation of renal pathology using light microscopy, recording the severity of findings.
• Assessment of common lesions: cast nephropathy, amyloidosis, renal calcification, microbial infection, and MM infiltration.

Main Results:

• Cast nephropathy was the most common lesion (n=27), followed by MM infiltration (n=17), amyloidosis (n=10), and renal calcification (n=5).
• MM infiltration incidence was higher than previously reported, detectable even with limited bone marrow plasmacytosis.
• Elevated serum creatinine correlated with severe cast nephropathy, but not MM infiltration. Higher MM infiltration was noted with liver invasion.

Conclusions:

• Severe cast nephropathy, not MM infiltration, is associated with elevated serum creatinine in MM patients.
• The high incidence of renal MM infiltration suggests it may be an under-recognized feature, especially with extramedullary disease.
• Findings provide insights into renal injury mechanisms and extramedullary disease in multiple myeloma.