Hypertrophic cardiomyopathy in identical twins.

Hypertrophic cardiomyopathy was diagnosed in identical twin boys in early childhood. One underwent myomectomy at the age of 12 years because of progressive severe exertional dyspnoea accompanied by considerable obstruction of the left ventricular outflow tract shown on both echocardiography and cardiac catheterisation. Seven years later, at the age of 19, he remains incapacitated to a moderate degree. By contrast, the other twin has led a relatively normal life to date and no left ventricular outflow obstruction has been shown.