[Diagnosis of amyloidosis].

The diagnosis of amyloidosis relies upon the demonstration of deposits exhibiting a characteristic yellow-green birefringence in Congo-red stained tissue section examined under polarization. Ultrastructural examination, demonstrating the specific fibrillar structure of amyloidosis is rarely necessary for diagnosis. The identification of the amyloid protein is made by immunohistochemistry on frozen tissue sections using specific antibodies directed against amyloid proteins: light chains of immunoglobulins, amyloid A protein, transthyretin.... In the absence of specific clinical symptoms, rectal submucosa biopsy and labial biopsy have a high sensitivity in the diagnosis of amyloidosis.