Lessons from rare cardiomyopathies: The importance of a phenotype-based approach to arrive at a specific diagnosis

The cardiomyopathies are disorders of the heart muscle, characterised by structural and functional abnormalities in the absence of haemodynamic conditions that solely explain the observed myocardial abnormality [1]. Since the first formal consensus on classification in 1980 [2], cardiomyopathies have been defined according to their morphological and physiological characteristics (e.g. ventricular hypertrophy or dilatation). More recent iterations have taken into account significant advances in our understanding and knowledge of the causes of cardiomyopathies by subdividing the morphological subtypes into familial/genetic and non-familial/non-genetic causes, but current classification schemes remain very much rooted in the identification of a clinical phenotype as the first step in the diagnostic pathway.