WBR0112
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Embryology, MainCategory::Genetics, MainCategory::Immunology |
| Sub Category | SubCategory::Cardiology |
| Prompt | [[Prompt::A newborn boy is found to be cyanotic following a natural birth. He is found to have Tetralogy of fallot and undergoes surgery which successfully corrects his cyanosis. Over the next few years, the boy suffers an unusually large number of sever bacterial infections. His pediatrician requests a chest x-ray and the radiologist noted absence of a thymic shadow. Which of the following is most likely to have cause this child’s condition?]] |
| Answer A | AnswerA::Abnormal development of the 1st branchial pouch |
| Answer A Explanation | AnswerAExp::Incorrect - DiGeorge syndrome is caused by abnormal development of the thrid and fourth branchial pouches. |
| Answer B | AnswerB::Abnormal development of the 2nd branchial pouch |
| Answer B Explanation | AnswerBExp::Incorrect - DiGeorge syndrome is caused by abnormal development of the third and fourth branchial pouches. |
| Answer C | AnswerC::Microdeletion on 7q |
| Answer C Explanation | AnswerCExp::Incorrect - Microdeleion of a region on 7q causes William’s Syndrome. |
| Answer D | AnswerD::Microdeletion on chromosome 15 |
| Answer D Explanation | AnswerDExp::Incorrect - Microdeletion of a region on chromosome 15 causes either Prader-Wili or Angelman’s syndromes. |
| Answer E | AnswerE::Microdeletion on chromosome 22 |
| Answer E Explanation | AnswerEExp::Correct - See explanation |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::The patient in this vignette is suffering from DiGeorge Syndrome or 22q.11 syndrome. DiGeorge syndrome is caused by the deletion of a small piece of chromosome 22. Patients suffer from cardiac abnormalities (40%), and conditions resulting from abnormal development of the third and fourth branchial pouches. The third and fourth branchial pouches give rise to the thymus and the parathyroid glands. As a result, patients experience hypocalcemia due to deficiency of parathyroid hormone and immunodeficiency of T cells due to lack of a thymus. Educational Objective: |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |