WBR0174
| Author | [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Alison Leibowitz)(Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Physiology |
| Sub Category | SubCategory::Gastrointestinal |
| Prompt | [[Prompt::A 2-year-old boy is brought to the pediatrics clinic by his mother for 2 months of noticeable fatigue. The mother reports that her child appears tired throughout the day, and that his most recent behavior has compelled her to seek help. She explains that she has, on several occasions, found her son chewing on small rocks in the backyard. On physical examination, you note a pale child with significant conjunctival pallor, and mild upward curving of the fingernails. Following complete work-up, you diagnose the child with iron deficiency anemia, and you prescribe oral iron supplementation. At which level of the GI tract would iron be absorbed?]] |
| Answer A | AnswerA::Duodenum |
| Answer A Explanation | AnswerAExp::The proximal duodenum is the predominant site of iron absorption. |
| Answer B | AnswerB::Stomach |
| Answer B Explanation | AnswerBExp::The stomach is not the site of iron absorption. |
| Answer C | AnswerC::Jejunum |
| Answer C Explanation | AnswerCExp::The jejunum is not the site of iron absorption. It is the site of folate absorption. |
| Answer D | AnswerD::Ileum |
| Answer D Explanation | AnswerDExp::The terminal ileum is the site of vitamin B12 absorption. |
| Answer E | AnswerE::Cecum |
| Answer E Explanation | AnswerEExp::The cecum is not the site of iron absorption. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The patient in this scenario has the classical presentation of iron deficiency anemia (IDA). Children are often asymptomatic but may present with fatigue, poor school performance, and pica (increased appetite for substances that are largely non-nutritive such as dirt, rocks, ice, and clay). Physical exam typically reveals tachycardia, impaired growth, skin and conjunctival pallor, spoon-shaped nails (koilonychia), and glossitis. Risk factors include prematurity, exclusive breastfeeding beyond 6 months not supplemented by iron-rich foods, early and/or excessive cow milk consumption, and maternal prenatal anemia.
Patients with IDA usually require several months of oral iron supplementation. Iron is absorbed in the duodenum as ferrous (Fe2+) iron. At physiological pH, ferrous iron is readily oxidized into ferric (Fe3+) iron, which is not as readily absorbed by the duodenum as ferrous iron. In vivo, however, the acidity present in the stomach allows the absorption of iron in the form of ferrous iron in the duodenum. The use of proton pump inhibitors, or other drugs that decrease gastric acidity may reduce the absorption of iron in the duodenum due to the decreased availability of ferrous iron. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Iron, WBRKeyword::Ferrous, WBRKeyword::Ferric, WBRKeyword::Duodenum, WBRKeyword::Absorption, WBRKeyword::IDA, WBRKeyword::Iron deficiency anemia, WBRKeyword::Anemia, WBRKeyword::Pica, WBRKeyword::Folate, WBRKeyword::Vitamin B12, WBRKeyword::Fatigue, WBRKeyword::Pallor |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |