A four year old boy was diagnosed with hypertrophic cardiomyopathy with
moderate degree of obstruction of the left ventricular outflow tract,
secondary to asymmetric septal hypertrophy and no features of congestive
heart failure, at the age of the 7 months. He was also found to have
myxomatous mitral valve, systolic anterior motion of anterior mitral
leaflet and moderate mitral regurgitation. There was no evidence of
ventricular septal defect at this point in time.In view of phenotypic
features suggestive of Noonan syndrome, he underwent genetic evaluation
with target gene sequencing and was detected to have a novel
heterozygous mutation in exon 13 of LZTR 1 (Leucine- zipper-like
transcriptional regulator 1) gene. Echocardiogram on follow up showed
increase in left ventricular outflow tract obstruction and appearance of
an aneurysm in the membranous portion of interventricular septum. There
were no features of right ventricular outflow obstruction, tricuspid
regurgitation or aortic regurgitation. 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. It is
an unusual mechanism for formation of membranous septal aneurysm, given
its absence in the earlier echocardiograms and absence of any left to
right shunt across the aneurysm. He has been initiated on beta blockers
due to severe left ventricular outflow tract obstruction and is planned
for septal myomectomy, resection of membranous septal aneurysm and
mitral valve repair.
Membranous septal aneurysm in a child with Noonan syndrome and hypertrophic cardiomyopathy
