WBR0109

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Author [[PageAuthor::William J Gibson (reviewed by Rim Halaby, M.D. [1])]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Genetics
Sub Category SubCategory::Renal
Prompt [[Prompt::A 40-year-old man presents to his local physician complaining of fatigue, malaise and constipation. The patient has undergone a 15 lbs weight loss over the past three months. The patient’s blood pressure is 140/100 mm Hg. Laboratory analysis is notable for a creatinine of 1.5 mg/dL and BUN of 25 mg/dL. Urinalysis reveals free red cells without casts. An MRI of the abdomen shows bilateral solid renal consolidations. Renal biopsy reveals dysplastic clear cells with several mitotic figures per high powered field. In which of the following genes does this patient most likely harbor a germline defect?]]
Answer A AnswerA::TSC1
Answer A Explanation [[AnswerAExp::Mutations of TSC1 cause tuberous sclerosis.]]
Answer B AnswerB::p53
Answer B Explanation [[AnswerBExp::Mutations of p53 cause Li-Fraumeni syndrome.]]
Answer C AnswerC::Rb
Answer C Explanation [[AnswerCExp::Mutations of Rb cause familial retinoblastoma.]]
Answer D AnswerD::PTEN
Answer D Explanation [[AnswerDExp::Mutations of PTEN cause Cowden syndrome.]]
Answer E AnswerE::VHL
Answer E Explanation [[AnswerEExp::VHL mutations increase the activity of the hypoxia inducible factor transcription factor (HIF). HIF increases the expression of many pro-angiogenic proteins to promote tumorigenesis. Bilateral renal cell carcinoma is highly specific for Von Hippel Lindau (VHL) syndrome, caused by mutations in the eponymous VHL gene.]]
Right Answer RightAnswer::E
Explanation [[Explanation::The patient in this vignette is experiencing the symptoms of renal compromise due to bilateral renal cell carcinoma. Bilateral renal cell carcinoma is highly specific for Von Hippel Lindau syndrome. Von Hippel–Lindau (VHL) disease is a rare, autosomal dominant genetic condition that predisposes individuals to benign and malignant tumors. The most common tumors found in VHL patients are clear cell renal carcinomas, central nervous system and retinal hemangioblastomas, pheochromocytomas, and pancreatic neuroendocrine tumors. The disease is caused by mutations of the von Hippel–Lindau tumor suppressor (VHL) gene on the short arm of chromosome 3. The VHL protein normally promotes the degradation of hypoxia inducible factor (HIF). These mutations cause constitutive signaling of hypoxia inducible factor, which increases the expression of certain essential pro-angiogenic proteins including VEGF.

Educational Objective: Bilateral renal cell carcinoma is highly specific for Von Hippel Lindau (VHL) syndrome, caused by mutations in the eponymous VHL gene.
References: First Aid 2014 page 87]]

Approved Approved::Yes
Keyword WBRKeyword::Von hippel lindau, WBRKeyword::Genetics, WBRKeyword::Cancer, WBRKeyword::Oncology, WBRKeyword::Autosomal dominant, WBRKeyword::Renal cell carcinoma, WBRKeyword::Kidney cancer, WBRKeyword::Tumor suppressor gene
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