Aortic root dilatation is a rare complication of Noonan syndrome.

Molecular analysis of the gene encoding the protein tyrosine phospatase, nonreceptor type 11 (PTPN11), identified a single base change at nucleotide 228 in an individual manifesting Noonan syndrome with aortic root widening and dysplastic aortic and mitral valves. This missense mutation changes glutamate to aspartate at position 76 of the protein (E76D or Glu76Asp), which likely disrupts intramolecular hydrogen bonding of this protein. There are few reports of aortic root dilatation in Noonan syndrome, and to our knowledge this is the first case with a confirmed PTPN11 mutation.