Transthyretin Gene Variants and Associated Phenotypes in Danish Patients with Amyloid Cardiomyopathy

Genotyping divides transthyretin cardiac amyloidosis (ATTR-CA) in hereditary (ATTRv) and wild type (ATTRwt) forms. This study investigated the prevalence and clinical presentation of ATTRv in a contemporary cohort of consecutive ATTR-CA patients diagnosed at a tertiary Danish amyloidosis center. Age at diagnosis, clinical- and echocardiographic data, and transthyretin (TTR) genotype were recorded. Relatives of ATTRv patients underwent clinical phenotyping and predictive gene testing. Genetic testing in 102 patients identified four TTR variant carriers: p.Pro63Ser, p.Ala65Ser (n = 2) and p.Val142Ile. The mean age of ATTRv index patients was significantly lower compared to ATTRwt patients: 70.2 +/- 1.2 versus 80.0 +/- 6.2, p-value: 0.005. Evaluation of ATTRv families identified seven TTR variant carriers with a median age of 65 years (range 48-76) and three were diagnosed with ATTR-CA by DPD-scintigraphy. Family members with ATTR-CA were all asymptomatic and had normal levels of cardiac biomarkers. In conclusion, the prevalence of ATTRv in a contemporary Danish ATTR-CA cohort is 4%. ATTRv index patients were significantly younger age at diagnosis than ATTRwt patients. Non-p.Leu131Met TTR variants have reduced penetrance at the age of 65 years in which approximately half of variant carriers have asymptomatic ATTR-CA with normal LV systolic function and cardiac biomarker analyses.