WBR0488
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathophysiology |
| Sub Category | SubCategory::Hematology |
| Prompt | [[Prompt::A 51 year old man presents to his primary care physician with complaints of pruritis especially following a warm or hot shower. The patient has noticed a recent increase in the intensity of the pruritis which he claims was very mild at first. He also reports recurrent headaches and episodes of dizziness especially in the past 3 months. On physical exam, the patient appears flushed with a ruddy complexion. The patient's blood pressure is elevated at 165/92 mmHg with splenomegaly noted on abdominal exam. Further investigation reveals significantly elevated hemoglobin at 17.4 g/dL. If the patient's condition is secondary to a genetic mutation, which of the following receptor types is likely involved?]] |
| Answer A | AnswerA::Receptor tyrosine kinase |
| Answer A Explanation | AnswerAExp::JAK2 is not a receptor tyrosine kinase. |
| Answer B | AnswerB::Non-receptor tyrosine kinase |
| Answer B Explanation | AnswerBExp::Polycythemia vera is due to a mutation in JAK2 a non-receptor tyrosine kinase. |
| Answer C | AnswerC::G-protein coupled receptor |
| Answer C Explanation | AnswerCExp::JAK2 is not part of the G-protein coupled receptor. |
| Answer D | AnswerD::Intracellular steroid receptor |
| Answer D Explanation | AnswerDExp::JAK2 is not part of the intracellular steroid receptor. |
| Answer E | AnswerE::Ion channel-associated receptor |
| Answer E Explanation | AnswerEExp::JAK2 is not part of an ion channel-associated receptor. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::Polycythemia vera (PV) is a is a myeloproliferative disorder characterized by excessive erythroid cell production. The massive increase in red blood cells leads to a higher blood viscocity accounting for the symptoms and complications of the disease. PV presents with pruritus secondary to an increase in histamine, skin discoloration, gouty arthritis, and thrombotic events associated with their constant hypercoagulable state. The majority of patients with PV (95%) have a mutation of JAK2, a non-receptor tyrosine kinase, that leads to hypersensitivity to erythropoeitin (EPO) signals and constituitive activation of EPO signaling even in the absence of EPO, with a concominant increase in RBC production. Treatment consists primarily of periodic phlebotomies to decrease blood viscocity and prevent complications.
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| Approved | Approved::No |
| Keyword | WBRKeyword::Polycythemia vera, WBRKeyword::JAK2 mutation |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |