Amyloidosis

Know the morphology of amyloidosis by light microscopy

• Deposits of amyloid appear in the gomerulus.

• First as subtle thickenings of the mesangial matrix

• Then as capillary narrowing and distortion of the capillary tufts as the basement membrane widens unevenly.

• Eventually lumens are obliterated and the obsolescent glomerulus is flooded by confluent masses or interlacing ribbons of amyloid

Know the special stains used for the detection of amyloid substance

• Congo red – appears red or pink

• Polarized light – green birefringence

Know the characteristics of amyloid fibrils by EM (Robbins, p.251)

• Made up largely of nonbranching fibrils of indefinite length and diameter of ~ 7,5 –10 nm

• Characteristic beta pleated sheet conformation allows for distinctive staining and birefringence properties, but is only observed by X-ray crystallography and infrared spectroscopy.

Category: Pathology Notes