Coexistence of hereditary transthyretin amyloid cardiomyopathy and sarcomeric hypertrophic cardiomyopathy: a multimodality imaging and genetic case report

Unexplained left ventricular hypertrophy (LVH) represents a diagnostic challenge, as phenotypic overlap may exist between sarcomeric hypertrophic cardiomyopathy (HCM) and infiltrative cardiomyopathies such as transthyretin amyloid cardiomyopathy (ATTR-CM). Multimodality imaging and genetic testing are crucial when standard findings are discordant.

A 78-year-old woman presented with exertional dyspnoea (NYHA class II) and asymmetric septal hypertrophy without secondary causes. Transthoracic echocardiography showed preserved left ventricular ejection fraction with reduced basal longitudinal strain and relative apical sparing. Cardiac magnetic resonance demonstrated elevated native T1 values (1240–1270 ms), mildly increased T2 values, and basal ring-like late gadolinium enhancement. Bone scintigraphy revealed Perugini grade 3 myocardial uptake, consistent with ATTR-CM. Monoclonal gammopathy was excluded. Genetic testing identified a pathogenic transthyretin mutation (TTR p.Ile88Leu) and a concomitant likely pathogenic sarcomeric MYH7 variant (p.Gly733Arg). Neurological assessment was unremarkable. The overall phenotype was dominated by amyloid infiltration.

Following multidisciplinary evaluation, the patient was started on tafamidis 61 mg once daily. Cascade genetic and clinical screening was recommended for first-degree relatives.