WBR263
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Will Gibson and Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | USMLE Step 1 |
| Main Category | Embryology |
| Sub Category | General Principles |
| Prompt | A 12-month-old girl is brought to the physician’s office with complaints of fever, vomiting, and difficulty breathing. The mother is a chronic alcoholic and had consumed alcohol excessively throughout the child’s pregnancy. Physical examination is remarkable for microcephaly, facial abnormalities, a heart murmur, and developmental delay. Which one of the following errors most likely occurred during the embryonic period? |
| Answer A | Aplasia |
| Answer A Explanation | Aplasia refers to the failure of an organ to develop despite the presence of primordial tissue. |
| Answer B | Hypoplasia |
| Answer B Explanation | Hypoplasia is incomplete organ development with the presence of primordial tissue. |
| Answer C | Agenesis |
| Answer C Explanation | Agenesis refers to the failure of an organ to develop due to the absence of primordial tissue. |
| Answer D | Deformation |
| Answer D Explanation | Deformation is extrinsic disruption of an organ or tissue; it occurs after the embryonic period. |
| Answer E | Malformation |
| Answer E Explanation | Alcohol exposure during pregnancy causes tissue and central nervous system malformations. The effects of alcohol in the CNS appear to be due in part to the negative effects on cell migration. |
| Right Answer | E |
| Explanation | Fetal alcohol syndrome is a leading cause of congenital malformation and intellectual disability in the United States. Newborns of mothers who consumed significant quantities of alcohol during pregnancy have an increased incidence of congenital abnormalities. These abnormalities include:
The child exhibits microcephaly, facial abnormalities, both of which are tissue malformations. The patient's heart murmur is likely also caused by tissue malformation, but echocardiography would be required for confirmation.
Malformation refers to the intrinsic disruption of tissue structure, and it typically occurs during the embryonic period of development (3rd -8th week). Alcohol, a teratogen, exerts its effect during this stage of fetal development. Defective cell migration is thought to mediate a substantial fraction of alcohol's teratogenicity. |
| Approved | Yes |
| Keyword | EtOH, Fetal Alcohol Syndrome, FAS, Alcohol, Teratogen, Substance abuse, Embryology, Embryo, Development |
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