Objective: Amyloidosis represents extracellular deposition of congophilic fibrils of similar morphology but different chemical composition. The types frequently involving the kidney are AA (serum amyloid A) and AL (light chain amyloid). Hereditary amyloidoses, which can also affect the kidney, are being described with increasing frequency. Distinguishing the type of amyloid is important because of the different treatments and outcomes. Typing of amyloidosis by immunohistochemistry (IHC) is believed to be unreliable, except for AA amyloid. We reevaluated our cases in this study to draw attention to the nonAA amyloid deposits in renal biopsies with amyloidosis.

Material and Method: Renal biopsies diagnosed as amyloidosis between 1997 and 2008 were stained for amyloid A with IHC. Cases with negative amyloid A staining were included in the study.

Results: We found 190 cases of renal amyloidosis (198 biopsies) during the study period. Thirty cases (33 biopsies) with negative antiAA staining were studied. Among those 30 cases with nonAA amyloidosis, secondary AL amyloidosis was due to multiple myeloma in 8 cases and plasma cell dyscrasia in 2 cases. Hereditary renal amyloidosis was suspected in some cases.

Conclusion: Using amyloid A IHC on a routine basis and the clinical history are essential to diagnose AA amyloidosis. The differential diagnosis of nonAA amyloidosis may be inconclusive on IHC. The diagnostic approach should be multidisciplinary and requires careful clinical and pathological evaluation. The limitation of IHC may necessitate direct typing of the amyloid protein extracted from paraffin-embedded specimens in some cases.