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|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. The unusually large number of infections in this patient is due to said T cell deficiency. | |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. The unusually large number of infections in this patient is due to said T cell deficiency. | ||
Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge syndrome, with the 22 to remind one the chromosomal abnormality is found on the 22 chromosome, as below:< | Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge syndrome, with the 22 to remind one the chromosomal abnormality is found on the 22 chromosome, as below: | ||
'''C'''ardiac Abnormality (especially [[tetralogy of Fallot]])<br />'''A'''bnormal [[Facies (medical)|facies]] <br />'''T'''hymic aplasia <br />'''C'''left palate <br />'''H'''ypocalcemia/'''H'''ypoparathyroidism. | |||
|AnswerA=Abnormal development of the 1st branchial pouch | |AnswerA=Abnormal development of the 1st branchial pouch | ||
|AnswerAExp=[[DiGeorge syndrome]] is caused by abnormal development of the third and fourth [[branchial pouches]]. | |AnswerAExp=[[DiGeorge syndrome]] is caused by abnormal development of the third and fourth [[branchial pouches]]. | ||
Revision as of 19:28, 29 March 2014
| Author | PageAuthor::William J Gibson |
|---|---|
| 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 a natural birth. He is diagnosed with tetralogy of Fallot and undergoes surgery that successfully corrects his cyanosis. Over the next few years, the boy suffers an unusually large number of severe bacterial infections. His pediatrician requests a chest x-ray and the radiologist notes an absence of the thymic shadow. Which of the following is most likely to have caused this child’s condition?]] |
| Answer A | AnswerA::Abnormal development of the 1st branchial pouch |
| Answer A Explanation | [[AnswerAExp::DiGeorge syndrome is caused by abnormal development of the third and fourth branchial pouches.]] |
| Answer B | AnswerB::Abnormal development of the 2nd branchial pouch |
| Answer B Explanation | [[AnswerBExp::DiGeorge syndrome is caused by abnormal development of the third and fourth branchial pouches.]] |
| Answer C | AnswerC::Microdeletion on 7q |
| Answer C Explanation | [[AnswerCExp::Microdeleion of a region on 7q causes William’s syndrome. The patient in this vignette has DiGeorge syndrome.]] |
| Answer D | AnswerD::Microdeletion on chromosome 15 |
| Answer D Explanation | [[AnswerDExp::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::DiGeorge syndrome is caused by a microdeletion on chromosome 22. |
| 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. The unusually large number of infections in this patient is due to said T cell deficiency.
Salient features can be summarized using the mnemonic CATCH-22 to describe DiGeorge syndrome, with the 22 to remind one the chromosomal abnormality is found on the 22 chromosome, as below: Cardiac Abnormality (especially tetralogy of Fallot) |
| 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:: |