Introduction
Noonan syndrome (NS) [Mendelian inheritance in man (MIM) # 163950] is a common autosomal dominant disease, with an estimated incidence rate of 1/1,000 to 1/2,500 live births1. It is characterized by obvious facial features, short stature, and congenital heart defects, mild to moderate developmental retardation/learning disabilities, skeletal abnormalities, cryptorchidism and myeloproliferative diseases2. It is an autosomal dominant disease with complete penetrance but variable expressiveness. About 50% of patients with NS have missense mutations in protein tyrosine phosphatase non-receptor type 11 (PTPN11) gene, with less mutations in SOS1, RAF1 and KRAS genes, accounting for 13%, 10% and less than 5% respectively3. About 30% of patients with clinically confirmed NS are still negative4. Intractable chylothorax in childhood is a rare and potentially life-threatening disease, with an incidence rate of about 1:30,0005. Associations with genetic syndromes include congenital lymphoid malformation syndromes such as Gorham-Stout, Optiz G/BBB, Hennekam, Milroy and NS, as well as chromosomal abnormalities such as Trisomy 21 or Turner syndrome6. Up to now, there is no reports about the refractory chylothorax due to thoracic duct stenosis in NS with RIT1 gene mutation.