In amyloidosis, there is extracellular deposition of fibrillar protein. This may be in a localized deposition or widely distributed throughout the body.
Amyloid fibrils stain with Congo red and show apple green birefringence in polarized light.
Cytotoxic and immunosuppressive drugs have been used to treat amyloidosis, but often with poor results. Improvement may be attained by treatment of an underlying cause.