A 63 year old woman presents with fatigue, numbness in her feet, and difficulty walking. Examination shows decreased vibration sense in both legs and a smooth beefy red tongue. Laboratory studies show hemoglobin 8.9 g/dL, MCV 112 fL, elevated homocysteine, and elevated methylmalonic acid. Which of the following reactions is most directly impaired?
- A)Pyruvate to acetyl CoA
- B)Phenylalanine to tyrosine
- C)Glucose 6 phosphate to 6 phosphogluconate
- D)Homocysteine to methionine and methylmalonyl CoA to succinyl CoAGABARITO
- E)Tryptophan to niacin
Explicação
This patient has vitamin B12 deficiency causing megaloblastic anemia and subacute combined degeneration. Cobalamin is required for methionine synthase and methylmalonyl CoA mutase, so both homocysteine and methylmalonic acid rise. The posterior column findings... Ver explicação completa e trilha adaptativa →