Unsuitable value of abdominal fat tissue aspirate examination for the diagnosis of amyloidosis in long-term hemodialysis patients.

Abdominal fat tissue aspiration was used in 22 long-term hemodialysis patients (5-17 years). Fourteen of these patients had carpal tunnel syndrome and amyloid deposits of beta 2-microglobulin in the synovium. One patient had a spontaneous rupture of the spleen with amyloid deposits in spleen vessels. Seven other patients presented carpal tunnel syndrome and/or articular pains, and radiological lytic lesions in bone, strongly suggesting an amyloid origin. As a control group, in 22 patients with biopsy-proven amyloidosis, abdominal fat tissue aspirates were performed and were studied under the same conditions: by light microscopy these tissues were stained with Congo red and examined with a polarizing microscope; these specimens were also studied by electron microscopy. In all hemodialyzed patients, no amyloid deposit was present in fat tissue with Congo red staining and by electron microscopy. On the contrary, amyloid was observed in 17 of 22 cases in other types of amyloidosis. It seems that this method which has been proved to be simple and sensitive for the diagnosis of systemic amyloidosis is not a good marker for the presence of amyloid in long-term hemodialysis patients.