WBR0469
| Author | [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::Gastrointestinal |
| Prompt | [[Prompt::A 6-month-old male is brought by his mother to the physician's office for failure to thrive and steatorrhea. Upon appropriate work-up, you diagnose him with abetalipoproteinemia. Which of the following genetic mutations is the primary defect in abetalipoproteinemia?]] |
| Answer A | AnswerA::Defect of LDL receptors |
| Answer A Explanation | [[AnswerAExp::A defect in LDL receptors frequently results in familial hypercholesterolemia (FH).]] |
| Answer B | AnswerB::Defect of apolipoprotein B |
| Answer B Explanation | [[AnswerBExp::Although apoB synthesis frequently decreases in individuals with abetalipoproteinema, an apoB defect is not the direct mutation that leads to abetalipoproteinema.]] |
| Answer C | AnswerC::Defect of microsomal triglyceride transfer protein |
| Answer C Explanation | [[AnswerCExp::A defect of the MTP gene (or MTTP) frequently results in abetalipoproteinemia.]] |
| Answer D | AnswerD::Defect of lipoprotein lipase |
| Answer D Explanation | [[AnswerDExp::A defect in lipoprotein lipase (LPL) frequently results in chylomicronemia]] |
| Answer E | AnswerE::Defect of chylomicron |
| Answer E Explanation | [[AnswerEExp::A defect in chylomicron is not the primary defect in individuals with abetalipoproteinemia, but often it occurs secondary to an MTP gene defect.]] |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::Abetalipoproteinemia, an inherited disorder characterized by fat accumulation in enterocytes, results in malabsorption of dietary fat and fat-soluble vitamins. Microsomal transfer proteins (MTP) are required for the creation of lipoproteins, such as VLDL, LDL, and chylomicrons. A defect of the MTP gene, located on the long arm of chromosome 4, results in abetalipoproteinemia.
Abetalipoproteinemia frequently manifests with GI, ocular, hematological, and neurological symptoms. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::abetalipoproteinemia, WBRKeyword::malabsorption, WBRKeyword::diarrhea, WBRKeyword::microsomal triglyceride transfer protein, WBRKeyword::enzymes, WBRKeyword::chylomicron, WBRKeyword::apolipoprotein, WBRKeyword::genetics, WBRKeyword::inheritance, WBRKeyword::mutation |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |