The analysis of gastrointestinal amyloidosis in 78 patients with chronic renal failure

Systemic amyloidosis is not a single disease, but the product of a variety of diseases. Amyloid proteins are insoluble fibrils that are deposited extracellularly in many organ tissues. They stain with Congo red and appear apple green under polarized light. Definitive diagnosis and classification of amyloidosis requires histologic examination of tissue samples. Gastrointestinal tract involvement is common, and all parts of the system can be affected. Immuno-histochemical studies have shown that amyloid deposited in the gastrointestinal system is most often of the AA, A kappa, or A lambda types. Another type of amyloid protein, beta-2 microglobulin (β2M), predominantly affects the musculoskeletal system, and is usually seen in patients who have been on long-term hemodialysis. Mixed systemic amyloidosis (β2M and AA) is seen only rarely in these patients. In this study, we attempted to answer why this is so, and examined whether or not mixed amyloidosis is related to amyloidogenesis. We studied gastrointestinal tissues from 78 chronic renal failure patients who had systemic amyloidosis with gastrointestinal involvement. A total of 115 endoscopic samples and 1 jejunal resection specimen were analysed immunohistochemically. Immunohistochemical testing using a panel of antisera directed against two major amyloid fibril proteins (AA-Monoclonal, Dako-, and β2 MPolyclonal, Dako-) showed that all samples contained AA amyloid, but not β2M type protein. These findings can be explained by the patients' relatively short average duration of hemodialysis and the predominance of endoscopic biopsy samples in our study.