Amyloid:
– A group of substances with B-pleeted sheet configuration.
– Eosnophilic appearance, located extracellularly proximate to basement membranes.
– Stain with Congo red, has apple green birefringence.
Clinical Patterns:
– Primary amylodisos (immuncytic dyscrasia): AL protein (derived from immuglobulin light chains) à deposits in heart, muscle, tongue, kidney.
– Associated with plasma cell disorders (multiple myeloma, waldenstrom macroglobulinemia).
– Secondary amyloidosis (ractive systemic): AA protein. Chronic tissue destruction à increase in SAA. (serum amyloid-associated protein)à deposition of fibrils consisting of amyloid protein (called AA protein) in parenchymous organs.
-“saga spleen”: perifollicular involvement resulting in a spleen that looks like tapioca granules.
Other forms:
– Portugeues type of polyneuropathy: derived from Transthyretin (a protein that transports thyroxine and retinol). Characterized by peripheral nerve involvment.
– Alzheimer disease: A4 amyloid (or AB-portein). Chromosome 21.
– Familial medicteranean fever: AA amyloid. Autosomal recessive disease.
– Medullary carcinoma of thyroid: Amyloid protein from calcitonin deposits within the tumor.
– Diabetes mellitus: amylin deposits in islet cells.
– Senile amyloidosis : found during autopsy in brain, heart. Transthyretin.
– Dialysis-associated : amyloid depsoits in joints. derived from B-microglobulin.