ClinVar

Description

The TTR c.148G>A; p.Val50Met variant (rs28933979), also known as Val30Met, is the most common pathogenic TTR variant associated with familial amyloidotic polyneuropathy worldwide (Parman 2016). The variant has a variable clinical presentation ranging from asymptomatic carriers to systemic disease, having early-late onset disease subtypes (Arvidsson 2015, Beirao 2015, Coelho 2017, Parman 2016). Functional studies suggest the variant refolds from monomers to tetramers at a slower rate compared to wildtype (Jesus 2016), has decreased stability in the folded state (Altland 2007), and impairs the inflammatory response necessary for nerve regeneration (Goncalves 2014). This variant is reported as pathogenic in ClinVar (Variation ID: 13417), and observed in the general population with an overall allele frequency of 0.01% (26/251462 alleles) in the Genome Aggregation Database. The valine at codon 50 is highly conserved, and computational analyses predict that this variant is deleterious (REVEL: 0.711). Additionally, other variants at this codon (p.Val50Ala, p.Val50Leu) have been reported in individuals with amyloid neuropathy and are considered pathogenic (Altland 2007, Suhr 2009). Based on available information, the p.Val50Met variant is considered to be pathogenic. References: Altland K et al. Genetic microheterogeneity of human transthyretin detected by IEF. Electrophoresis. 2007 Jun;28(12):2053-64. PMID: 17503405. Arvidsson S et al. Amyloid Cardiomyopathy in Hereditary Transthyretin V30M Amyloidosis - Impact of Sex and Amyloid Fibril Composition. PLoS One. 2015 Nov 23;10(11):e0143456. PMID: 26600306. Beirao JM et al. Ophthalmological manifestations in hereditary transthyretin (ATTR V30M) carriers: a review of 513 cases. Amyloid. 2015;22(2):117-22. PMID: 26096568. Coelho T et al. Clinical measures in transthyretin familial amyloid polyneuropathy. Muscle Nerve. 2017 Mar;55(3):323-332. PMID: 27422379. Goncalves NP et al. The inflammatory response to sciatic nerve injury in a familial amyloidotic polyneuropathy mouse model. Exp Neurol. 2014 Jul;257:76-87. PMID: 24800914. Jesus CS et al. A New Folding Kinetic Mechanism for Human Transthyretin and the Influence of the Amyloidogenic V30M Mutation. Int J Mol Sci. 2016 Aug 31;17(9). PMID: 27589730. Parman Y et al. Sixty years of transthyretin familial amyloid polyneuropathy (TTR-FAP) in Europe: where are we now? A European network approach to defining the epidemiology and management patterns for TTR-FAP. Curr Opin Neurol. 2016 Feb;29 Suppl 1:S3-S13. PMID: 26734951. Suhr OB et al. Report of five rare or previously unknown amyloidogenic transthyretin mutations disclosed in Sweden. Amyloid. 2009 Dec;16(4):208-14. PMID: 19922332.