WBR0544
| Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Genetics, MainCategory::Microbiology, MainCategory::Pathology |
| Sub Category | SubCategory::Neurology |
| Prompt | [[Prompt::A 14-year-old male is brought to the physician's office by his mother for recent-onset headache, vomiting, and ataxia. Following appropriate work-up, the patient is found to have hemangioblastoma in the cerebellum and renal cell carcinomas bilaterally. Genetic testing leads to a diagnosis. Which of the following findings is most likely associated with the patient's condition?]] |
| Answer A | AnswerA::Hematocrit (Hct) = 58 % |
| Answer A Explanation | AnswerAExp::Polycythemia is associated with VHL. |
| Answer B | AnswerB::Serum sodium = 122 mmol/L |
| Answer B Explanation | AnswerBExp::Hyponatremia is not frequently associated with VHL. |
| Answer C | AnswerC::Serum alanine aminotransaminase (ALT) = 241 IU/L |
| Answer C Explanation | AnswerCExp::Elevated ALT is not frequently associated with VHL. |
| Answer D | AnswerD::Platelet count = 43,000 per microliter |
| Answer D Explanation | AnswerDExp::Thrombocytopenia is not frequently associated with VHL. |
| Answer E | AnswerE::Serum calcium = 13 mmol/L |
| Answer E Explanation | AnswerEExp::Hypercalcemia is not frequently associated with VHL. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The patient has von Hippel-Lindau (VHL) disease, an autosomal dominant disorder caused by germline mutation of one copy of the VHL tumor suppressor gene on chromosome 3. VHL is characterized by hemangioblastomas of the retina, cerebellum, and medulla. Also patients frequently present with bilateral renal cell carcinomas or other tumors, such as pheochromocytomas. A common manifestation of VHL in young patients are headaches with neurological symptoms. Symptoms of other tumors may also manifest, such as hypertension in the case of pheochromocytoma.
The VHL gene product, E3 ubiquitin ligase, which normally targets hypoxia-inducible factor (HIF) in the presence of oxygen for destruction, is absent in VHL. As a result, polycythemia is a finding associated with VHL, due to the overproduction of hypoxia-induced factor (HIF). |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::von hippel lindau, WBRKeyword::polycythemia, WBRKeyword::hematocrit, WBRKeyword::HCT, WBRKeyword::hemangioblastoma, WBRKeyword::bilateral renal cell carcinoma, WBRKeyword::headache, WBRKeyword::vomiting, WBRKeyword::pheochromocytoma, WBRKeyword::hypoxia induced factor, WBRKeyword::HIF, WBRKeyword::autosomal, WBRKeyword::autosomal dominant, WBRKeyword::genetics, WBRKeyword::genes, WBRKeyword::pattern of inheritance, WBRKeyword::inheritance, WBRKeyword::mutation, WBRKeyword::deletion |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |