Longterm complete remission of AL-amyloid-related nephrotic syndrome

We describe a 59-year-old man with nephrotic syndrome that was diagnosed as suspected minimal change nephrotic syndrome by the routine examination of renal tissues at first biopsy, because renal histology showed segmental mild mesangial expansion with argyrophilic staining and partial foot process fusion without any deposition. Prednisolone therapy induced complete remission of nephrotic syndrome. Relapse occurred after 4 years of complete remission, and the second renal biopsy revealed amyloid light-chain (AL)-amyloidosis. Re-examination of the first biopsy tissues by Congo red staining confirmed a small amount of amyloid deposition in the mesangial areas although the mesangial areas showed argyrophilic staining, which is atypical for amyloid deposition. This case raises a caution that even when renal histology is not suggestive of amyloidosis and prednisolone therapy is very effective, when a renal histology diagnosis is not confirmed, the clinician should suspect amyloidosis and should, at least, undertake Congo red staining to definitively rule out amyloidosis.