Unusual hypertrophic cardiomyopathy: case report of an early onset wild-type ATTR amyloidosis accompanied by a chromosomal duplication involving the MYH6 and MYH7 gene

To date, no other case featuring wild-type transthyretin amyloidosis (wtATTR) concurrently with a chromosomal duplication affecting both cardiac myosin heavy chain genes has been reported in the literature. This highlights the extreme rarity of this condition, making it challenging to ascertain the extent to which a presumably mutated hybrid myosin gene construct or the TTR amyloid fibrils contribute to stiffness, tissue fibrosis, and cardiac dysfunction. Ultimately, both effects converged in this case, leading to the same cardiac disease with an exacerbated phenotypical outcome of hypertrophic cardiomyopathy (HCM). While early onset wtATTR is an uncommon clinical finding, another significant clinical condition was identified in this patient, marked by an unusual copy number variation (CNV) in the genes <i>MYH6</i> and <i>MYH7</i>.