WBR284

Author	[[PageAuthor::Gerald Chi (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	USMLE Step 1
Main Category	Pathology
Sub Category	Cardiology
Prompt	A newborn boy is evaluated for vomiting when fed for the first time. Physical examination is remarkable for flat facies, an unusually large tongue, and prominent epicanthal folds. Upper gastrointestinal studies demonstrate gas in the stomach and the duodenal bulb. Which of the following cardiovascular defects is mostly associated with his newborn's underlying genetic disease?
Answer A	Ectopic ductal tissue
Answer A Explanation	Coarctation of the aorta, which is commonly associated with Turner syndrome, results from ectopic ductal tissue or from abnormal development of the fourth and sixth aortic arch.
Answer B	Improper alignment of aorticopulmonary septum
Answer B Explanation	Tetralogy of Fallot is caused by improper alignment of aorticopulmonary septum.
Answer C	Failure of aorticopulmonary septum to twist
Answer C Explanation	Transposition of the great vessels is caused by failure of aorticopulmonary septum to twist and is commonly present in children of diabetic mothers.
Answer D	Inadequate formation of the septum secundum
Answer D Explanation	Ostium secundum atrial septal defect (ASD) is the most common type of ASD. It arises from inadequate growth of the septum secundum and comprises up to 10% of all cases of congenital heart diseases. Although ASD is associated with Down syndrome, endocardial cushion defects are more common.
Answer E	Inadequate migration of neural crest cells
Answer E Explanation	Failure of migration of neural crest cells to the endocardial cushion is the most common congenital heart disease associated with Down syndrome.
Right Answer	E
Explanation	The patient is most likely diagnosed with Down syndrome (trisomy 21), as evidenced by the phenotypic profile, Down syndrome is associated with duodenal atresia, which is characterized by the congenital underdevelopment of parts of the duodenum and is suggested by the vomiting and the double bubble sign on imaging. Down syndrome is strongly associated with an increased risk of congenital cardiovascular disease, especially endocardial cushion defects (AV canal). Down syndrome is also associated with other congenital heart diseases (less commonly than with endocardial cushion defects), namely ventricular septal defects (VSD) and atrial septal defects (ASD). Educational Objective: Down syndrome is strongly associated with endocardial cushion defects (formation of AV canal), which is characterized by failure of migration of neural crest cells to the endocardial cushion. References: FIrst Aid 2015 page 290.
Approved	Yes
Keyword	Down syndrome, AV canal, Endocardial cushion defect
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