Pediatric-onset HCM is rare and associated with adverse outcomes driven mainly by arrhythmic events. Risk extends well beyond adolescence, which calls for unchanged clinical surveillance into adulthood. In this study, predictors of adverse outcomes differ from those of adult populations with HCM. In secondary prevention, the implantable cardioverter defibrillator did not confer absolute protection in the presence of limiting symptoms of heart failure.

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Background - The X-linked Danon disease (DD) manifests by severe cardiomyopathy, myopathy, and neuropsychiatric problems. We designed this registry to generate a comprehensive picture of clinical presentations and outcome of patients with Danon disease (DD) in cardiomyopathy centers throughout Europe. Methods - Clinical and genetic data were collected in 16 cardiology centers from 8 European countries. Results - The cohort comprised 30 male and 27 female patients. The age at diagnosis was birth to 42 yr. in males and 2-65 in females. Cardiac involvement was observed in 96%. Extracardiac manifestations were prominent in males but not in females. Left ventricular (LV) hypertrophy was reported in 73% of male and 74% of female patients. LV systolic dysfunction was reported in 40% of males (who had LVEF 34±11%) and 59% of females (LVEF 28±13%). The risk of arrhythmia and heart failure (HF) were comparable among genders. The age of first HF hospitalization was lower in males (18 ± 6 vs. 28 ±17 yr., p<0.003). HF was the leading cause of death (10/17, 59%), and LV systolic dysfunction predicted an adverse outcome. Eight males and 8 females (28%) underwent heart transplantation or received a left ventricular assist device (LVAD). Our cohort suggests better prognosis of female compared to male heart transplant recipients. Conclusions - DD presents earlier in males than females and runs a malignant course in both genders, due to cardiac complications. Cardiomyopathy features: heart failure and arrhythmia, are similar among the genders. Clinical diagnosis and management is extremely challenging in females due to phenotypic diversity and absence of extracardiac manifestations.