The clinicopathological spectrum of renal amyloidosis.

BACKGROUND

Renal amyloidosis is an uncommon cause of nephrotic syndrome. The clinical conditions in Chinese people remain obscure. This is a retrospective review of the clinicopathological spectrum of 12 cases diagnosed in Taichung Veterans General Hospital from October 1982 to November 1993.

METHODS

Charts and renal pathological slides were reviewed retrospectively. A scoring system was set to evaluate the degree of amyloid deposition in the renal tissue. The clinical profile, immunological data, pathological picture and final outcomes are presented and discussed, with literature review.

RESULTS

There were 12 cases of primary amyloidosis including 1 case of multiple myeloma. All were confirmed by renal biopsy. The cases were all male with mean age of onset as 53.3 +/- 11.3 (range: 32 to 65 years). The mean follow-up duration was 22.9 +/- 32.8 months. The initial average creatinine clearance was 66.7 +/- 42.7 ml/min; mean daily urine protein was 7.0 +/- 4.1 grams. Nephrotic syndrome was the main clinical manifestation, present in all 12 cases. Other presenting symptoms and signs included: malaise in 7 cases; hypertension and anorexia in 4 cases; limb numbness in 3 cases; low back pain, dizziness and microhematuria in 2 cases each; anemia, headache, stroke, restrictive cardiomyopathy, hepatomegaly, syncope, body weight loss, dysphagia and skin itching in one case individually. Amyloid cardiomyopathy was present in 4 of the 8 patients who received echocardiography. The mean serum albumin level was 1.9 +/- 0.7 mg/dl, globulin level 3.1 +/- 1.1 mg/dl. Urinary Bence-Jones protein examination was performed in 8 cases; none revealed positive response. The mean immunoglobulin (Ig) level for the patients included: IgG 1018 +/- 901 mg/dl, IgA 262.0 +/- 313.8 mg/dl, IgM 104.8 +/- 84.2 mg/dl. There were at least 4 cases with high levels of one Ig but depressed levels in the others. M-component was shown by immunoelectrophoresis (IEP) in 90% of the cases. IEP impression in 10 cases revealed 2 cases of IgA lambda, 2 cases IgA kappa, 3 cases IgG lambda and 1 case IgG kappa monogammopathy, 1 case free lambda myeloma and 1 case negative. The ratio of kappa to lambda chain was 3:6. Bone marrow biopsy performed in 8 cases found only 1 case with multiple myeloma, one with amyloidosis; the other 6 cases were unremarkable. Mesangium was the site of heaviest amyloid deposition, followed by tubular basement membrane, artery and interstitium. The median survival time for those whose total score was lower than 3 points was 97.5 months; 3 to 5 points, 14 months; 6 points or more, 18.5 months. The median survival time was 21.6 months and 3-year-survival rate was 32.7%. The 2 cases with long-term survival were of 111 months and 84 months. The possible reason included: 1) Organ-limited renal amyloidosis; 2) Light amyloid deposition; 3) Younger age; 4) Other undetected favorable factors.

CONCLUSIONS

1. Renal amyloidosis is not a frequent diagnosis of nephrotic syndrome in Taiwan, but it should be suspected in every patient over 50 years old with a recent onset of proteinuria. 2) Renal amyloidosis can be diagnosed only by renal biopsy. 3) Primary renal amyloidosis is a disease of poor prognosis.