WBR0139

Author	[[PageAuthor::William J Gibson (Reviewed by Alison Leibowitz [1] and Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 9-year-old boy is brought by his mother to the physician's office with complaints of recurring infections. On physical examination, the physician observes that the patient has low set ears and eyes that appear abnormally far apart. According to the child growth chart, the patient is underweight for his age. Upon further questioning, the mother explains that the patient experienced difficulty gaining weight as a child. Following appropriate work-up, genetic testing reveals a deletion in the long arm of chromosome 22. Abnormalities of which embryological structure is most commonly associated with this patient's condition?]]
Answer A	AnswerA::Truncus arteriosus
Answer A Explanation	[[AnswerAExp::The truncus arteriosus, which gives rise to the ascending aorta and the pulmonary trunk, often forms abnormally in patients with DiGeorge syndrome, leading to a persistent truncus arteriosus.]]
Answer B	AnswerB::Bulbus cordis
Answer B Explanation	[[AnswerBExp::The bulbus cordis, which is a segment of the primitive heart tube, gives rise to the right ventricle and the smooth part of the left ventricle. Bulbus cordis abnormalities are not classically associated with DGS.]]
Answer C	AnswerC::Sinus venosum
Answer C Explanation	[[AnswerCExp::The sinus venosum gives rise to the coronary sinus. Abnormalities of the sinus venosum are not classically associated with DGS.]]
Answer D	AnswerD::Third aortic arch
Answer D Explanation	[[AnswerDExp::Abnormalities of the third aortic arch, which gives rise to to the common carotid artery and the proximal part of the internal carotid artery, are not associated with DGS.]]
Answer E	AnswerE::Fourth aortic arch
Answer E Explanation	[[AnswerEExp::Abnormalities of the fourth aortic arch, which gives rise to the proximal part of the right subclavian artery on the right side and the aortic arch on the left side, are not associated with DGS.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::DiGeorge syndrome (DGS) is characterized by the deletion of chromosome 22q11.2. Deletions on chromosome 22 often manifest with defects in neural crest migration with aberrant development of the 3rd and the 4th brachial pouches. Patients with DGS often have CATCH: Conotruncal abnormalities, Abnormal facies, Thymic hypo/aplasia (T cell deficiency), Cleft palate, and Hypocalcemia (no development of parathyroid glands). Cardiac abnormalities associated with DGS include tetralogy of Fallot, pulmonary atresia, VSD, interrupted aortic arch, and persistent truncus arteriosus. The truncus arteriosus, which gives rise to the ascending aorta and the pulmonary trunk .Patients with DGS may develop persistent truncus arteriosus, a condition in which the aorticopulmonary septum has not formed (pictured below). Oxygenated blood from the left ventricle mixes with deoxygenated blood from the right and is pumped into both the lungs and systemic circulation through one great vessel. These children are cyanotic at birth and require urgent surgical intervention. Educational Objective: DiGeorge syndrome is associated with persistent truncus arteriosus. References: Carotti A, Digilio MC, Piacentini G, et al. Cardiac defects and results of cardiac surgery in 22q11.2 deletion syndrome. Dev Disabil Res Rev. 2008;14(1):35-42. First Aid 2014 page 91]]
Approved	Approved::Yes
Keyword	WBRKeyword::Cardiology, WBRKeyword::Conotruncal abnormalities, WBRKeyword::Thymic aplasia, WBRKeyword::Thymic hypoplasia, WBRKeyword::Embryology, WBRKeyword::Congenital, WBRKeyword::Genetics, WBRKeyword::Neural crest, WBRKeyword::DiGeorge syndrome, WBRKeyword::Chromosome, WBRKeyword::CATCH, WBRKeyword::CATCH-22, WBRKeyword::CATCH 22, WBRKeyword::Chromosomal abnormality, WBRKeyword::Craniofacial, WBRKeyword::Heart defect
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