Progressively worsening hypertrophic cardiomyopathy in a child with newly diagnosed Costello syndrome while receiving growth hormone therapy.

We describe a 6-year-old boy with newly diagnosed Costello syndrome after the diagnosis of severe hypertrophic cardiomyopathy. His neonatal asymmetric septal cardiomyopathy resolved by 9 months of age but reappeared at 6 years of age. This report highlights two important concepts: the association of genetic syndromes with hypertrophic cardiomyopathy and the possibility of worsening severity of hypertrophic cardiomyopathy linked to growth hormone therapy.