WBR0112: Difference between revisions
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|SubCategory=Cardiology, Infectious Disease | |SubCategory=Cardiology, Infectious Disease | ||
|Prompt=A newborn boy is found to be cyanotic following birth. Appropriate work-up is performed; and the patient is diagnosed with tetralogy of Fallot. In the patient's pre-operative chest x-ray, the radiologist notes an absence of the thymic shadow. The patient then undergoes surgery that successfully corrects his cyanosis. Over the next few days, he suffers a seizure that is attributed to low calcium blood levels. Which of the following abnormalities most likely caused this child’s condition? | |Prompt=A newborn boy is found to be cyanotic following birth. Appropriate work-up is performed; and the patient is diagnosed with tetralogy of Fallot. In the patient's pre-operative chest x-ray, the radiologist notes an absence of the thymic shadow. The patient then undergoes surgery that successfully corrects his cyanosis. Over the next few days, he suffers a seizure that is attributed to low calcium blood levels. Which of the following abnormalities most likely caused this child’s condition? | ||
|Explanation=[[DiGeorge syndrome]] or 22q.11 syndrome is caused by the microdeletion within chromosome 22q11 that results in the abnormal embryological development of the third and the fourth branchial | |Explanation=[[DiGeorge syndrome]] or [[22q.11 syndrome]] is caused by the [[microdeletion]] within chromosome 22q11 that results in the abnormal embryological development of the third and the fourth [[branchial pouch]]es. These pouches normally give rise to the [[thymus]] and the [[parathyroid glands]]. | ||
Patients with DiGeorge syndrome suffer from congenital heart disease, especially conotruncal malformations (such as tetralogy of Fallot, interrupted aortic arch, ventricular septal defect, and truncus arteriosus), characteristic facial features, thymic hypoplasia | Patients with DiGeorge syndrome suffer from congenital heart disease, especially conotruncal malformations (such as [[tetralogy of Fallot]], [[interrupted aortic arch]], [[ventricular septal defect]] ([[VSD]]), and [[truncus arteriosus]]), characteristic facial features, and [[thymic hypoplasia]], which is characterized by loss of thymic shadow on chest x-ray and results in T-cell immune deficiency and susceptibility to overwhelming infections. Also patients with DiGeorge syndrome often have palatal abnormalities (such as [[velopharyngeal incompetence]], [[cleft palate]], or [[bifid uvula]]), and underactive parathyroid gland causing [[hypocalcemia]] and hypocalcemia-induced seizures in the neonatal period. | ||
Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge syndrome:<br /> | Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge syndrome:<br /> | ||
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|AnswerC=Presence of a Barr body | |AnswerC=Presence of a Barr body | ||
|AnswerCExp=Presence of [[Barr body]], an inactive X chromosome in a female somatic cell, is a normal finding only in women. X chromosomes are inactivated by a process called [[lyonization]]. | |AnswerCExp=Presence of [[Barr body]], an inactive X chromosome in a female somatic cell, is a normal finding only in women. X chromosomes are inactivated by a process called [[lyonization]]. | ||
|AnswerD=Abnormal development of | |AnswerD=Abnormal development of the branchial pouch responsible for the development of the thymus only | ||
|AnswerDExp=The 3rd branchial pouch is responsible for the development of the inferior parathyroid glands (dorsal wings) and the thymus (ventral wings). However, the 3rd branchial pouch is not the only | |AnswerDExp=The 3rd branchial pouch is responsible for the development of the inferior parathyroid glands (dorsal wings) and the thymus (ventral wings). However, the 3rd branchial pouch is not the only involved branchial pouch in DiGeorge syndrome. The 4th branchial pouch, which is responsible for the development of the superior parathyroids (dorsal wings), is also involved. | ||
|AnswerE=A microdeletion | |AnswerE=A microdeletion | ||
|AnswerEExp=[[DiGeorge syndrome]] is caused by a microdeletion within chromosome 22. | |AnswerEExp=[[DiGeorge syndrome]] is caused by a microdeletion within chromosome 22. | ||
Revision as of 21:28, 9 September 2014
| Author | [[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D. and Rim Halaby, M.D. [1])]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Embryology, MainCategory::Genetics, MainCategory::Immunology |
| Sub Category | SubCategory::Cardiology, SubCategory::Infectious Disease |
| Prompt | [[Prompt::A newborn boy is found to be cyanotic following birth. Appropriate work-up is performed; and the patient is diagnosed with tetralogy of Fallot. In the patient's pre-operative chest x-ray, the radiologist notes an absence of the thymic shadow. The patient then undergoes surgery that successfully corrects his cyanosis. Over the next few days, he suffers a seizure that is attributed to low calcium blood levels. Which of the following abnormalities most likely caused this child’s condition?]] |
| Answer A | AnswerA::Abnormal development of the 1st and 2nd branchial pouches |
| Answer A Explanation | [[AnswerAExp::DiGeorge syndrome is caused by abnormal development of the 3rd and 4th branchial pouches.]] |
| Answer B | AnswerB::Abnormal development of the 2nd and 3rd branchial pouches |
| Answer B Explanation | [[AnswerBExp::DiGeorge syndrome is caused by abnormal development of the 3rd and 4th branchial pouches.]] |
| Answer C | AnswerC::Presence of a Barr body |
| Answer C Explanation | [[AnswerCExp::Presence of Barr body, an inactive X chromosome in a female somatic cell, is a normal finding only in women. X chromosomes are inactivated by a process called lyonization.]] |
| Answer D | AnswerD::Abnormal development of the branchial pouch responsible for the development of the thymus only |
| Answer D Explanation | [[AnswerDExp::The 3rd branchial pouch is responsible for the development of the inferior parathyroid glands (dorsal wings) and the thymus (ventral wings). However, the 3rd branchial pouch is not the only involved branchial pouch in DiGeorge syndrome. The 4th branchial pouch, which is responsible for the development of the superior parathyroids (dorsal wings), is also involved.]] |
| Answer E | AnswerE::A microdeletion |
| Answer E Explanation | [[AnswerEExp::DiGeorge syndrome is caused by a microdeletion within chromosome 22.]] |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::DiGeorge syndrome or 22q.11 syndrome is caused by the microdeletion within chromosome 22q11 that results in the abnormal embryological development of the third and the fourth branchial pouches. These pouches normally give rise to the thymus and the parathyroid glands.
Patients with DiGeorge syndrome suffer from congenital heart disease, especially conotruncal malformations (such as tetralogy of Fallot, interrupted aortic arch, ventricular septal defect (VSD), and truncus arteriosus), characteristic facial features, and thymic hypoplasia, which is characterized by loss of thymic shadow on chest x-ray and results in T-cell immune deficiency and susceptibility to overwhelming infections. Also patients with DiGeorge syndrome often have palatal abnormalities (such as velopharyngeal incompetence, cleft palate, or bifid uvula), and underactive parathyroid gland causing hypocalcemia and hypocalcemia-induced seizures in the neonatal period. Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge syndrome: |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Immunodeficiency, WBRKeyword::Genetics, WBRKeyword::T cell, WBRKeyword::Thymus, WBRKeyword::Infection. Cardiology, WBRKeyword::Tetralogy of Fallot |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |