WBR0124

Author	PageAuthor::William J Gibson
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biochemistry, MainCategory::Genetics, MainCategory::Histology
Sub Category	SubCategory::Hematology
Prompt	[[Prompt::A 9 year old girl is brought by her parents to the emergency room for abdominal pain and pain in her left thigh. The pain developed over the past several days, and today she was unable to walk because of it. She has a history of anorexia, and abdominal bloating for the past several years. She recalls one previous incident of pain in her thigh. On physical exam, the abdomen is distended, the spleen palpable 4 cm below the costal margin and the liver tender to mild palpation. The left thigh retains full range of motion, but is painful with knee extension and deep palpation. There is no family history of sickle cell anemia/trait and the patient tests negative for HbS by hemoglobin electrophoresis. Peripheral blood smear reveals marked microcytosis with anisocytosis. Bone marrow biopsy confirms the diagnosis with the visualization of “tissue paper” macrophages pictured below. Which of the following is the most likely underlying genetic lesion in this patient? ]]
Answer A	AnswerA::Mutation in HFE
Answer A Explanation	AnswerAExp::'''Incorrect''' - This gene is mutated in hereditary hemochromatosis.
Answer B	AnswerB::Deficiency of Glucocerobrosidase
Answer B Explanation	AnswerBExp::'''Correct''' – This is the mutated gene in Gaucher’s disease.
Answer C	AnswerC::Deficiency of Galactocerebrosidase
Answer C Explanation	AnswerCExp::'''Incorrect''' – This gene is mutated in Krabbe’s disease.
Answer D	AnswerD::Deficiency of Alpha-Galactosidase A
Answer D Explanation	AnswerDExp::'''Incorrect''' – This gene is mutated in Fabry’s disease.
Answer E	AnswerE::Deficiency of Hexosaminidase A
Answer E Explanation	AnswerEExp::'''Incorrect''' – This gene is mutated in Tay-Sach’s disease.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Gaucher's disease is a genetic disease in which a fatty substance (lipid) accumulates in cells and certain organs. Gaucher's disease is the most common of the lysosomal storage diseases. It is a form of sphingolipidosis (a subgroup of lysosomal storage diseases), as it involves dysfunctional metabolism of sphingolipids. The disorder is characterized by bruising, fatigue, anemia, low blood platelets, and enlargement of the liver and spleen. Wiki keyword association: “Tissue Paper Macrophages” == Gaucher’s Disease Educational Objective: Gaucher's disease is caused by a deficiency of Glucocerebrosidase. References: First Aid 2012 page 116 Educational Objective: References: ]]
Approved	Approved::Yes
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