The place of type I familial amyloid neuropathy in amylosis. Anatomo-clinical study of a case in France]

The clinical and pathologic findings of a case of amyloidogenic heredo familial neuropathy type I is presented. The patient is a man, died at 46 years. The examination of a nerve biopsy, the clinical evolution and the family history are representative of the condition. The study of autopsy material revealed amyloïd deposits within vessels walls, autonomic nerves of almost all viscera but liver, muscle and skin, around myofibers in the heart. Kidney glomeruli were markedly involved and numerous obsolescent glomeruli were seen. Lesions of central nervous system were of interest: enlargement of meningeal vessels walls due to amyloïd deposits as subpial deposition band were observed. The pattern of amyloïd deposits within peripherical nerves was quite different according to their proximal or distal ends. While distal amyloïd deposits were scant, nerve damages were striking. In proximal portions, amyloïdosis could be found in all layers of nerve structures including the walls of endoneural small vessels. Semi-thin sections allowed to observe rare myelinated fibers entrapped by aggregates of a microfibrillary material. While there was absence of a patent axonal lesion, clusters of regenerating fibers were not infrequent. Ultrastructural study confirmed the close relationship between amyloïd fibrils, Schwann cell basal laminae and collagen fibers. An immunopathological study using immunserums raised against the AA composant of amyloïdosis, K and lambda light chains, and prealbumin were negative. Our results are in agreement with descriptions already reported in the medical literature. Therefore, they allow to discuss already known pathogenic mechanisms for this rare affection transmitted by a dominant autosomic gene.