Primary Amyloidosis

Supplemental Studies

Congo Red positive with apple-green birefringence
- Fluorescence microscopy of Congo red stain using rhodamine filter may improve sensitivity
Electron microscopy shows non-branching fibrils witih twisted beta-pleated sheet conformation
Immnohistochemistry, in situ hybridization or flow cytometry may prove clonality of associated plasma cell population
Immunostaining for kappa versus lambda light chain restriction in amyloid deposits often has high background in paraffin embedded tissue

Serum or urine protein electrophoresis, immunofixation, light chain quantification
Quantitation and typing of monoclonal immunoglobulin / light chain
Serum free light chain analysis may be required to demonstrate clonal light chains
These studies may be used to
- Establish presence of a monoclonal plasma cell population
- Quantitation helps subtype the plasma cell dyscrasia (i.e. >3g/dL serum monoclonal protein is a major criterion for myeloma)
- Track disease burden over time