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NBME 21 Answers

nbme21/Block 1/Question#45

An 18-year-old man comes to the physician because ...

Pyruvate kinase

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 +4  upvote downvote
submitted by est88(10),

Pyruvate Kinase defect leads to decreased ATP leading to rigid RBCs and extra vascular hydrolysis. Increased levels of 2,3-BPG decreases hemoglobin affinity for O2.

For this one you just had to know the glycolysis pathway. Stem told you 2,3-BPG is elevated, which is upstream of pyruvate kinase.

neonem  Right, and that glycolytic enzyme deficiencies lead to hemolytic anemias. +2  
toxoplasmabartonella  I just thought the typical presentation of pyruvate kinase deficiency would be hemolytic anemia of the newborn. +2  

 +1  upvote downvote
submitted by h0odtime(15),
  • Normocytic Intrinsic Hemolytic Anemia: Reticulocyte >>2.5%
  • PEP --> Pyruvate (last step of Glycolysis) second ATP producing step
  • Mature RBC require pyruvate kinase without it they depend on the anaerobic generation of ATP
  • With insufficient ATP, all active processes in the cell come to a halt. Sodium potassium ATPase pumps are the first to stop: increase intracellular K+, water leaves cell with Na+. Cell Shrinks & dies. Body is deficient in RBC + destroyed by lack of ATP = Hemolytic Anemia
  • Inheritance: AR
b1ackcoffee  ermm . buddy, stopping NaKATPase causes RISE in intracellular Na, cell SWELLS and dies. +