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Mesangial glomerulopathy and IgM rheumatoid factor in rheumatoid arthritis
1Department of Internal Medicine, School of Medicine, University of California, Davis.
Abstract:
Hematuria and proteinuria in rheumatoid arthritis (RA) are commonly associated with drug therapy but occur independently of drugs, amyloid or urologic disorders. The latter occurrences suggest a primary renal lesion associated with RA. Review of reported renal biopsies identifies mesangial glomerulopathy as a common finding in RA patients without associated drug therapy and that it is frequently associated with hematuria in nonrheumatoid patients. Moreover, immunoglobulins have been shown to concentrate in the mesangium in experimental animals, suggesting that a functional response by the kidney mesangium to remove IgM rheumatoid factor (RF)-IgG complexes could lead to this mesangial lesion. We describe 3 patients with RA who had a mesangiopathy characterized by increased quantities of mesangial matrix and deposition of IgM without other lesions. Together, these observations suggest that: (1) mesangial glomerulopathy is common in RA; (2) removal of circulating RF-IgG complexes is a function of the mesangium and might produce this renal lesion; (3) mesangial glomerulopathy may be responsible for much of the hematuria observed in RA patients and, in many cases, may not be drug related and thus may not require discontinuing beneficial therapy.
Insights
Rheumatoid arthritis (RA) patients often experience kidney issues like hematuria. A primary renal lesion, mesangial glomerulopathy, may cause these symptoms by processing immune complexes, independent of drug treatments.
Area of Science:
- Nephrology
- Rheumatology
- Immunology
Background:
- Hematuria and proteinuria in rheumatoid arthritis (RA) are often attributed to drug side effects.
- However, these renal manifestations can occur independently of medications, suggesting an intrinsic kidney involvement in RA.
Observation:
- A review of renal biopsies revealed mesangial glomerulopathy as a frequent finding in RA patients not on drug therapy.
- This condition was also associated with hematuria in non-rheumatoid patients.
- Experimental studies show immunoglobulins concentrating in the kidney's mesangium.
Findings:
- Three RA patients presented with mesangiopathy, characterized by increased mesangial matrix and IgM deposition without other renal lesions.
- This suggests the kidney mesangium may play a role in removing immune complexes, potentially leading to this lesion.
- Mesangial glomerulopathy appears to be a common renal finding in RA.
Implications:
- Mesangial glomerulopathy may account for significant hematuria in RA patients.
- This renal lesion may not be drug-related, potentially allowing for the continuation of beneficial RA therapies.
- Understanding this primary renal lesion is crucial for managing RA patients with kidney involvement.