A 68-year-old man with hypertension and atrial fibrillation was referred to the heart failure department for dyspnoea; he had clinical signs of right heart failure. Results of neurological clinical examination and electromyogram were normal. Doppler echocardiography showed concentric hypertrophy of the left ventricle, with an ejection fraction of 37% ( Appendix A: Video 1 ). The two atria were enlarged ( Appendix A: Video 1 ). The mitral valves were thickened, causing mitral regurgitation ( Appendix A: Video 1 ). Transmitral flow showed a restrictive pattern and systolic pulmonary artery pressure was estimated at 54 mmHg. A magnetic resonance imaging (MRI) scan showed widespread post-gadolinium delayed enhancement in the left ventricular wall and atria, suggesting amyloidosis ( Figs. 1 and 2 ). Standard biological examination, protide electrophoresis and immunofixation were normal, as was a salivary gland biopsy. Myocardial biopsies of the right ventricle were performed. Several immunostaining tests were performed on these cardiac biopsies: the Congo red dye test showed diffuse dark-red cardiac amyloid deposits (image not shown). Under polarized light the amyloid proteins glowed green with this red dye test (image not shown). Transthyretin (TTR) immunostaining was strongly positive ( Fig. 3 ), whereas the light chain (kappa and lambda) immunostaining test was negative. Full sequencing of the TTR gene showed a new heterozygote pathogenic mutation: TTR-Thr-75-Ile.
