Membranous septal aneurysm in a child with Noonan syndrome and hypertrophic cardiomyopathy

A 4-year-old boy was diagnosed with hypertrophic cardiomyopathy with moderate degree of obstruction of the left ventricular outflow tract, secondary to asymmetric septal hypertrophy during infancy. Echocardiogram on follow-up showed increase in left ventricular outflow tract obstruction and appearance of an aneurysm in the membranous portion of interventricular septum. The appearance of the membranous septal aneurysm may be related to the direction of jet arising from the point of contact of the anterior mitral leaflet with the hypertrophied basal septum and hitting this part of the interventricular septum.