WBR0107

Author	[[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D. and Rim Halaby, M.D. [1])]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Genetics
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 22-year-old man presents to the primary care physician's office for a complaint of progressive hearing loss. He works as an elementary school teacher and reports he often cannot hear when students ask him questions during class. Upon further questioning, the patient reports he had an unusual event one week ago that he describes as a moving sensation "as if the whole world was spinning". Several similar episodes ensued since then. Two days before presentation, the patient also noticed he started to have a ringing sound in his ears that he cannot attribute to any particular cause. The patient denies pain, recent ear infections, or discharge. Following appropriate work-up, the physician orders a head MRI (shown below). What is the mode of inheritance of this patient's most likely condition? ]]
Answer A	AnswerA::Autosomal recessive
Answer A Explanation	[[AnswerAExp::Neurofibromatosis type 2 is autosomal dominant. An example of an autosomal recessive disease is Severe Combined Immunodeficiency.]]
Answer B	AnswerB::Autosomal dominant
Answer B Explanation	AnswerBExp::Neurofibromatosis type 2 is an autosomal dominant disease.
Answer C	AnswerC::X-linked recessive
Answer C Explanation	[[AnswerCExp::Neurofibromatosis type 2 is autosomal dominant. An example of an X-linked recessive disease is Duchenne muscular dystrophy.]]
Answer D	AnswerD::X-linked dominant
Answer D Explanation	[[AnswerDExp::Neurofibromatosis type 2 is autosomal dominant. An example of an X-linked recessive disease is Rett syndrome.]]
Answer E	AnswerE::Mitochondrial
Answer E Explanation	[[AnswerEExp::Neurofibromatosis type 2 is autosomal dominant. An example of an X-linked recessive disease is Myoclonic Epilepsy with Ragged Red Fibers.]]
Right Answer	RightAnswer::B
Explanation	[[Explanation::The patient in this vignette has neurofibromatosis type II (NF II). The main manifestation of NF II is the development of bilateral, symmetric, non-malignant brain tumors in the region of the cranial nerve (CN) VIII. Theses tumors are called vestibular schwannomas (acoustic neuromas). Because they grow in the region of CN VIII, patients may develop hearing difficulties, tinnitus and balance disturbances. NF II is also known as (or "MISME Syndrome", for "Multiple Inherited Schwannomas, Meningiomas, and Ependymomas") due to the predilection for these other brain tumors to form in patients. An example of a patient with bilateral acoustic neuromas (left panel) and meningiomas (right panel) is shown below. More than 90% of NF II patients suffer eye lesions. The most common alteration in NF II is the juvenile subcapsular cataract (opacity of the lens) in young people. NF II is caused by mutations of the NF2 gene coding for the "Merlin" protein. "Merlin" localizes to adherens junctions, but its tumor suppressive properties remain poorly understood. The principal treatments consist of neurosurgical removal of the tumors and surgical treatment of the eye lesions. Educational Objective: Neurofibromatosis type 2 is an autosomal dominant disease. References: First Aid 2014 page 87; First Aid 2012 page 90]]
Approved	Approved::Yes
Keyword	WBRKeyword::Cancer, WBRKeyword::Genetics, WBRKeyword::Tumor suppressor gene, WBRKeyword::Tumor suppressor, WBRKeyword::Inheritance, WBRKeyword::Autosomal dominant, WBRKeyword::Oncology
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