Multimodality Imaging Reveals Rare Hereditary Transthyretin Amyloidosis Mimicking Hypertrophic Cardiomyopathy.

BACKGROUND: Distinguishing hypertrophic cardiomyopathy from phenocopies remains a diagnostic challenge in younger patients presenting with unexplained ventricular hypertrophy. CASE SUMMARY: A 52-year-old Moroccan woman previously diagnosed with nonobstructive hypertrophic cardiomyopathy presented with recurrent pericardial chest pain, poorly tolerating angiotensin-converting enzyme inhibitors and beta-blockers. Cardiac magnetic resonance showed asymmetric hypertrophy and papillary muscle hypertrophy suggestive of hypertrophic cardiomyopathy, with markedly elevated native T1 mapping and extracellular volume. Bone scintigraphy subsequently demonstrated intense cardiac tracer uptake, consistent with transthyretin cardiac amyloidosis. Genetic testing confirmed a rare pathogenic TTR variant, p.Lys35Asn. Neurologic evaluation revealed moderate to severe sensorimotor polyneuropathy. Disease-modifying therapy with vutrisiran was initiated within a multidisciplinary care program. DISCUSSION: Current cardiomyopathy guidelines emphasize the importance of recognizing systemic red flags in hypertrophic phenotypes. Multimodality imaging is critical to establish diagnosis of transthyretin cardiac amyloidosis and allow timely initiation of disease-modifying therapy. TAKE-HOME MESSAGE: Unexplained hypertrophy with systemic manifestations should prompt evaluation for transthyretin amyloidosis.