Incidence of nonamyloidogenic mutations in the transthyretin gene in patients with autonomic and small fiber neuropathy.

INTRODUCTION: Mutations of the transthyretin (TTR) gene have been associated with polyneuropathy; the protein product has a tendency to form amyloid deposits in the peripheral nervous system. METHODS: Patients with small fiber neuropathy (SFN) with or without autonomic symptoms were given skin biopsies to assess nerve fiber density. Any patient with autonomic symptoms was assessed for autonomic neuropathy (AN). If testing revealed no clear cause of neuropathy, the TTR gene was sequenced. RESULTS: Thirty-six percent of patients were found to harbor at least 1 mutation in the TTR gene sequence (variants of unknown significance [VUS]). Of 24 patients diagnosed with SFN, 8% of patients had a point mutation (c76G>A). Of those patients who were diagnosed with both SFN and AN, 68% of patients had a VUS within the TTR gene (c76G>A, c337-18G>C). CONCLUSIONS: The results suggest an association between presumed nonamyloidogenic mutations in the TTR gene and the development of AN and SFN. Muscle Nerve 57: 140-142, 2017.