WBR0885
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Embryology |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::A child born to a 28 year old homeless woman is transferred to the neonatal intensive care unit directly after birth for treatment of respiratory distress. Although the mother had several personal difficulties in the past months, she reports that the pregnancy was smooth and she always followed up at community healthcare facility. After the infant was stabilized, the physician proceeds with an initial physical examination. At first, his exam seems unremarkable, but the physician soon notices a small tuft of hair of the infant's lower back. The most likely associated congential anomaly in this patient is an example of which of the following?]] |
| Answer A | AnswerA::Agenesis |
| Answer A Explanation | AnswerAExp::Ageneis refers to absent organ development due to absent primordial tissue |
| Answer B | AnswerB::Malformation |
| Answer B Explanation | AnswerBExp::Malformation refers to an error that occurs anywhere during the embryonic period between 3 to 8 weeks of embryogenesis. |
| Answer C | AnswerC::Deformation |
| Answer C Explanation | AnswerCExp::Deformation is an enbryologic defect that occurs after 8 weeks. |
| Answer D | AnswerD::Aplasia |
| Answer D Explanation | AnswerDExp::Aplasia is absent organ development despite the presence of primordial tissue. |
| Answer E | AnswerE::Migration defect |
| Answer E Explanation | AnswerEExp::Migration defects are classically seen with neural crest cells. Examples include aotricopulmonary septum formation defects and Hirschprung disease. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::Several embryologic anomalies in organ development and maturation can be encountered. Typically the anomalies are classified according to either the presence or absence of primordial tissue or the time period during which they most likely occur. In general, 5 common error can be described. Malformation refers to an error that occurs anywhere during the embryonic period between 3 to 8 weeks of embryogenesis. A deformation is anything that occurs after 8 weeks. Before 3 weeks defects are usually fatal.
In terms or primordial tissue, agenesis refers to absent organ development due to absent primordial tissue, while aplasia is absent organ development despite the presence of primordial tissue. Hypoplasia refers to incomplete organ development. Spina bifida is a neural tube defect by which the bony spinal canal fails to close completely due to the failure of the neuropores to close at 4 weeks of development. It usually presents with a tuft of hair on the lumbar area. Spina bifida is a classical example of a malformation.
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| Approved | Approved::No |
| Keyword | WBRKeyword::Malformation, WBRKeyword::spina bifida |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |