Systemic Amyloidoses in Renal Biopsy Samples

Summary

The kidneys are one of the most frequent sites of amyloid deposition during systemic AL, AA, and several hereditary amyloidoses. Distinguishing between different forms of amyloids is clinically important because of their different treatment.

Material and methods:
We present a 5-year retrospective study of amyloidoses diagnosed in renal biopsy samples. The classification of amyloidosis was made by immunofluorescence and immunohistochemical staining with antibodies to kappa and lambda immunoglobulin light chains, and for serum amyloid A protein.

Results:
From January 2003 to December 2007, 996 renal biopsy samples from one centre were evaluated. Amyloidosis was diagnosed in 62 samples (6.2%); 33 (53.2%) were classified as AL and 25 (40.3%) as AA amyloidosis. Four cases have remained unclassified. We did not identify any difference in the distribution of deposits among cases with AL and AA amyloidosis, respectively. The majority of patients underwent the renal biopsy due to severe proteinuria or nephrotic syndrome. Three patients had very low proteinuria, less than 0.5g/day. Diagnosis of amyloidosis was suspected by nephrologists in 48 patients (77.4%).

Conclusion:
Diagnosis of amyloidosis involves detection of amyloid deposits and classification of the amyloid form, which represent the basic step for appropriate therapy. Alltogether it is not an easy task for pathologists, and with the emergence of markedly different treatments depending on the specific type of amyloid, the precise typing is of increasing clinical importance and should be performed with great care. Immunofluorescence can be very useful in daily practice for classification of the type of amyloidosis.

Key words:
systemic amyloidosis - diagnosis of amyloidosis - renal amyloidosis