Long-term outcome according to renal histological lesions in 118 patients with monoclonal gammopathies.
BACKGROUND
The prognosis of monoclonal gammopathies with multiple myeloma and renal involvement is poor, and the indication for renal replacement therapy is controversial. Few studies address the value of renal histology for determining prognosis according to initial pathology findings.


METHODS
We studied the course of 118 patients with multiple myeloma according to renal biopsy lesions. The monoclonal component was identified and quantified in serum and urine. Tumor cell mass was classified as stage 1, 2 or 3, according to Durie and Salmon. End-points were death, or survival on dialysis, or serum creatinine level at last examination.


RESULTS
Renal biopsy showed myeloma kidney in 48 cases (41%), AL-amyloidosis in 35 (30%), light chain deposit disease in 22 (19%), chronic tubulointerstitial nephritis in 12 (10%) and cryoglobulinaemic kidney with multiple myeloma in 1. Maintenance haemodialysis was required in 46 patients (39%), earlier (P<0.0001) in myeloma kidney (mean: 3 months after diagnosis) than in AL-amyloidosis (mean: 15 months) and light chain deposit disease (mean: 18 months). Median survival was 12 months in myeloma kidney, 24 months in AL-amyloidosis and 48 months in light chain deposit disease. Dialysis increased survival in light chain deposit disease, in contrast with myeloma kidney and AL-amyloidosis patients whose survival was shorter when dialysed. The main cause of death during first year of dialysis was cardiac involvement in AL-amyloidosis, and sepsis or cardiac insufficiency in myeloma kidney. There was a trend to increased survival with multidrug chemotherapy which seemed to slow progression to end-stage renal failure. At last follow-up (median: 12 months, range 1-297), 65 (55%) patients had died. By multivariate analysis, independent predictors of survival were: age < 70, serum creatinine < or = 300 micromol/l, and serum calcium < or = 2.5 mmol/l.


CONCLUSIONS
Initial renal biopsy helps predict prognosis in patients with multiple myeloma and renal involvement. Maintenance haemodialysis is a reasonable indication in light chain deposit disease and AL-amyloidosis, especially in patients aged < 70. Multidrug therapy tends to prolong survival and slow progression to end-stage renal disease.