This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic and genetic disorders, Subject name: Pediatrics
A child presents with antimongoloid slant, pulmonary stenosis, sho stature, and undescended testis. The likely diagnosis is _____ 
Select and explain. 
A. Hypoparathyroidism, B. Noonan syndrome, C. Klinefelter syndrome, D. XYY sex chromosome
B: Noonan syndrome
Answer: B: Noonan syndrome 
Explanation: The child presenting with the antimongoloid slant, pulmonary stenosis, sho stature, and undescended testis is suggestive of Noonan syndrome. Noonan syndrome: Autosomal-dominant disorder (12q) Male or female with Turner phenotype; normal karyotype Clinical features: Down-slanting palpebral fissure (antimongoloid slant) Pectus carinatum Hypeelorism Cryptorchidism Low levels of clotting factor 11 and 12 Leukemia (Juvenile chronic myelogenous leukemia) Moderate mental retardation in 25% Cardiac abnormality: Most common is pulmonary valve stenosis Hyperophic cardiomyopathy Atrial septal defect Coarctation of aoa Sho stature, webbed neck, low set ears, cubitus valgus: Similarities with Turner syndrome Ptosis, micrognathia, Clinodactyly, delayed pubey Difference between Noonan syndrome and Turner&;s syndrome: Noonan syndrome Turner Syndrome Normal karyotype (46XX/46XY) 45,XO(60%) Most common hea disease: Valvular pulmonary stenosis Most common hea disease: Bicuspid aoic valve 25% have mental retardation Mental retardation rare Genitourinary: Genitourinary: Female: Feile, delayed pubey Female: Infeile, Streak ovaries Male: Infeile due to cryptorchidism No males Ref: nelson textbook of pediatrics 21st edition Pgno: 669,2995