Decreasing incidence of AA amyloidosis in Spain

The main objectives of our study were to review all cases of amyloidosis diagnosed by renal biopsy in Spain from 1994 to 2009 and to analyse variations in the incidence over time.

We analysed all biopsies from native kidneys included in the Spanish Registry of Glomerulonephritis. A total of 120 centres provided 17 680 biopsies over 16 years. Follow-up was divided in four periods.

We collected 653 cases of renal amyloidosis. In 438 cases (67%), amyloidosis type was specified, [AA amyloidosis, 253 cases (57·8%); AL amyloidosis, 185 cases (42·2%)]. Mean age was 60 (17·8) years; 51·4% of patients were younger than 65. Overall incidence was 3·7%. In patients < 65, AA amyloidosis was present in 66·1% and AL amyloidosis in 33·9% (P < 0·01). No differences were found in patients > 65. Patients with AA amyloidosis were younger (56·8 vs. 64·0, P < 0·01) and had worse creatinine clearance (35 vs. 57 mL/min, P < 0·01). We found a decrease in the incidence among biopsies collected during each of the 4 study periods (4·2%, 3·9%, 3·5% and 3·2%, respectively, P < 0·001).

This is the largest series of renal amyloidosis in kidney biopsies published to date. We found amyloidosis to be decreasing slowly in Spain. This decrease affects both types and is confirmed in all cases marked in patients < 65 and in AA type. AA amyloidosis was the most frequent in our series. Patients affected by it were younger and had worse kidney function, with no differences in the level of proteinuria.