Rapid progression of mitral valve disease in a child with Noonan syndrome.

Noonan syndrome is the second most common genetic syndrome associated with congenital heart disease after Trisomy 21. The two most common cardiac lesions associated with Noonan syndrome are pulmonary stenosis and hypertrophic cardiomyopathy. Although the incidence of mitral valve disease in Noonan syndrome ranges between 2 and 6%, rapid progression of mitral valve dysplasia causing severe mitral valve regurgitation and left atrial dilatation is seldom seen. Most cases of mitral valve disease have been diagnosed either on routine echocardiographic surveillance or when presented with heart failure symptoms. We describe an 18-month-old boy with Noonan syndrome presenting in atrial flutter due to a massively enlarged left atrium caused by severe mitral valve regurgitation which developed and progressed in less than 17 months.