WBR0139

Author	[[PageAuthor::William J Gibson,(Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Embryology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 9-year-old boy is brought to the emergency department 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 chromosome 22. Of the following embryological structures, which would most likely form abnormally in individuals who have the same chromosomal abnormality as this patient?]]
Answer A	AnswerA::Truncus arteriosus
Answer A Explanation	[[AnswerAExp::The patient in this scenario presents with findings characteristic of DiGeorge syndrome. DiGeorge syndrome is characterized by the deletion of 22q11.2. Deletions on chromosome 22 often manifest with defects in neural crest migration. The truncus arteriosus, which gives rise to the ascending aorta and the pulmonary trunk, often forms abnormally in patients with DiGeorge syndrome, leading to the additional diagnosis of persistent truncus arteriosus, which is caused by the deletion in chromosome 22q11.2.]]
Answer B	AnswerB::Bulbus cordis
Answer B Explanation	[[AnswerBExp::The Bulbus cordis, which gives rise to the right ventricle and the smooth part of the left ventricle, is not associated with DiGeorge syndrome.]]
Answer C	AnswerC::Sinus venosum
Answer C Explanation	[[AnswerCExp::The sinus venosum gives rise to the coronary sinus.]]
Answer D	AnswerD::Third aortic arch
Answer D Explanation	[[AnswerDExp::The third aortic arch, which gives rise to to the common carotid artery and the proximal part of the internal carotid artery, is not associated with DiGeorge syndrome.]]
Answer E	AnswerE::Fourth aortic arch
Answer E Explanation	[[AnswerEExp::The fourth aortic arch, which gives rise to the proximal part of the right subclavian artery is not associated with DiGeorge syndrome.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::The patient in this scenario presents with findings characteristic of DiGeorge syndrome. DiGeorge syndrome is characterized by the deletion of chromosome 22q11.2. Deletions on chromosome 22 often manifest with defects in neural crest migration. The truncus arteriosus, which gives rise to the ascending aorta and the pulmonary trunk, often forms abnormally in patients with DiGeorge syndrome due to dysfunction of cardiac neural crest cells. These patients 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 the both the lungs and systemic circulation through one great vessel. These children are cyanotic at birth and require surgical intervention. Educational Objective: DiGeorge syndrome is associated with persistent truncus arteriosus. References: First Aid 2014 Page 212]]
Approved	Approved::Yes
Keyword	WBRKeyword::Cardiology, WBRKeyword::Embryology, WBRKeyword::Congenital, WBRKeyword::Genetics, WBRKeyword::Neural crest, WBRKeyword::DiGeorge syndrome, WBRKeyword::Chromosome, WBRKeyword::Chromosomal abnormality, WBRKeyword::Craniofacial, WBRKeyword::Heart defect
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