[Demonstration of genetic mutation in most of the amyloid neuropathies with sporadic occurrence].

The Portuguese type of familial amyloid polyneuropathy (FAP type I) is a disabling autosomic dominant disorder, which is caused by a point mutation in the transthyretin (TTR) gene. Other TTR gene mutations have been reported recently in other FAP. In the absence of monoclonal gammopathy, sporadic amyloid neuropathies raise a problem for their pathogenicity. In this study, we have looked for TTR gene mutations in apparently sporadic cases of amyloid polyneuropathy by Southern's technique. All the patients were of french origin. None had monoclonal gammopathy. The mean age at onset was 64 (50 to 79 years). Most of the patients (9/1) were male. Five patients were found to carry FAP type 1 mutation, and 2 the tyr 77 (German) mutation. This study suggests that investigations in amyloid polyneuropathy with no overt family history should include systematic DNA analysis.