WBR0488
| Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathophysiology |
| Sub Category | SubCategory::Hematology |
| Prompt | [[Prompt::A 51-year-old man presents to the physician's office with worsening pruritus for the past 3 months. He reports that his pruritus becomes much worse following a hot shower. On review of systems, the patient also complains of recurrent headaches for the past few weeks. His temperature is 37.1 °C (98.8 °F), blood pressure is 165/92 mmHg, and heart rate is 88/min. Physical examination is remarkable for facial plethora, engorged conjunctival veins, and splenomegaly palpated 3 cm below costal margin. Further investigation reveals hemoglobin of 18.8 g/dL. The physician suspects a genetic disorder and confirms the diagnosis with genetic testing. Which of the following receptor types is most likely involved in this patient's condition?]] |
| 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 manifests 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 myeloproliferative disorder characterized by excessive erythroid cell production. The massive increase in red blood cells leads to a higher blood viscosity, accounting for the symptoms and complications of the disease. PV manifests with pruritus, secondary to an increase in histamine, skin discoloration, gouty arthritis, and thrombotic events associated with a hypercoagulable state. The majority of patients with PV (95%) have a mutation of JAK2, a non-receptor tyrosine kinase. This mutation leads to hypersensitivity to erythropoeitin (EPO) signals and constitutive activation of EPO signaling, even in the absence of EPO, with a concomitant increase in RBC production. Treatment consists primarily of periodic phlebotomies to decrease blood viscosity and prevent complications. Educational Objective: Polycythemia vera manifests due to a mutation in JAK2 a non-receptor tyrosine kinase. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Polycythemia vera, WBRKeyword::JAK2 mutation, WBRKeyword::genetics, WBRKeyword::inheritance, WBRKeyword::lesion, WBRKeyword::dermatology, WBRKeyword::skin, WBRKeyword::arthritis, WBRKeyword::RBC, WBRKeyword::genome, WBRKeyword::abnormality |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |