Amyloid heart disease mimicking hypertrophic cardiomyopathy*

OBJECTIVE: To investigate the importance of transthyretin (TTR) gene mutations in explaining the phenotypic expression in patients diagnosed with hypertrophic cardiomyopathy (HCM) in northern Sweden. BACKGROUND: Hypertrophic cardiomyopathy is relatively common and often caused by mutations in sarcomeric protein genes. Mutations in the TTR gene are also common, one of which causes familial amyloid polyneuropathy (FAP), with peripheral polyneuropathy and frequently, cardiac hypertrophy. These circumstances were highlighted by the finding of an index case with amyloidosis, presenting itself as HCM. Initial rectal and fat biopsies did not show amyloid deposits. Later on, the patient was shown to carry a TTR gene mutation, and cardiac amyloidosis was confirmed by myocardial biopsy. Only then was a repeated fat biopsy positive for amyloid deposits. DESIGN: Cross-sectional study. SETTING: Cardiology tertiary referral centre. SUBJECTS: Forty-six unrelated individuals with HCM and the index case were included. Common diagnostic criteria for HCM were used. The 46 patients with HCM were previously analysed for mutations in eight sarcomeric protein genes and the TTR gene was now analysed by denaturing high-performance liquid chromatography and direct sequencing. RESULTS: One mutation in the TTR gene (Val30Met) was found in three individuals and the index case. CONCLUSIONS: Three of the 46 cases with HCM carried the Val30Met mutation, and were considered likely to have cardiac amyloidosis, like the index case. As a correct diagnosis of cardiac amyloidosis is mandatory for a potentially life-saving treatment, TTR mutation analysis should be considered in cases of HCM not explained by mutations in sarcomeric protein genes.