Prevalence of hereditary transthyretin amyloid polyneuropathy in idiopathic progressive neuropathy in conurban areas

BACKGROUND: Hereditary transthyretin amyloidosis (ATTR amyloidosis) is a rare, genetically heterogenous, and clinically variable autosomal dominant disease that severely reduces life expectancy. As treatment options grow, a proper diagnostic approach is mandatory especially in non-endemic regions with diverse genetic backgrounds. METHODS: We examined 102 neuropathy patients at a German neuromuscular centre. Common causes of polyneuropathy were ruled out by medical history and extensive laboratory testing to define a cohort of patients with progressive polyneuropathy classified as idiopathic. Molecular genetic testing of the entire TTR gene was performed, and the detected amyloidogenic and non-amyloidogenic variants were associated with the observed clinical phenotypes and results of prior diagnostic testing. RESULTS: Two of 102 patients tested positive for amyloidogenic mutations (p.Ile127Val and p.Glu81Lys), while a variant of unknown significance, p.Glu26Ser, was found in 10 cases. In both positive cases, previous negative biopsy results were proved by gene sequencing to be false negative. In case of the p.Glu81Lys mutation we detected clinical presentation (combination of severe polyneuropathy and cardiomyopathy), ethnic background (patient of polish origin, mutation only reported in Japanese families before), and disease course clearly differed from well-known cases of the same mutation in the literature. CONCLUSIONS: In conclusion, transthyretin hereditary amyloid polyneuropathy (ATTR-PN) should be considered in cases of otherwise idiopathic polyneuropathy. Sequencing of the four exons of the TTR gene should be considered the key step in diagnosis, while tissue biopsy possibly leads to false negative results.