[A case of nephrotic syndrome associated with minimal renal amyloidosis--a four-year follow-up].

A 61-year-old male had nephrotic syndrome in association with minimal renal amyloidosis. The amyloid deposits were inconspicuous and had been initially overlooked, and the biopsy specimen was thought to show minimal glomerular changes. Accordingly he was diagnosed as having minimal change nephrotic syndrome (MCNS). Thereafter, administration of 40 mg/day of prednisolone was started. A few weeks after treatment, proteinuria decreased, but did not disappear. Four years later, he was readmitted for the treatment of the nephrotic syndrome. The second biopsy at 65 years of age revealed typical renal amyloidosis by light microscopy. Congo red staining and electron microscopy confirmed the presence of amyloid deposits. The serum A protein (SAA) level was 328 micrograms/ml. Furthermore, the first biopsy specimen revealed minimal renal amyloidosis by Congo red staining. At the time, 40 mg/day of prednisolone proved ineffective for the proteinuria. However, after methylprednisolone pulse therapy, the proteinuria decreased and the nephrotic syndrome improved. After discharge, administration of 20 mg/day of prednisolone was maintained. One year later, the patient showed no evidence of recurrence of the nephrotic syndrome and the SAA level decreased (from 328 micrograms/ml to 74.4 micrograms/ml). Prednisolone proved to have a beneficial effect on the reduction of proteinuria and SAA levels. We strongly recommend careful examination for amyloid deposits in all kidney biopsy specimens with the appearance of MCNS on older patients whose proteinuria does not respond to the administration of prednisolone.