A 29 year old woman with severe rheumatoid arthritis develops fatigue and oral ulcers 2 months after starting a new medication. Laboratory studies show hemoglobin 9.8 g/dL, MCV 108 fL, normal methylmalonic acid, and elevated homocysteine. Which of the following enzymes is most likely inhibited by the medication causing her anemia?
- A)Thymidylate synthase
- B)Xanthine oxidase
- C)Dihydrofolate reductaseGABARITO
- D)Hypoxanthine guanine phosphoribosyltransferase
- E)Adenosine deaminase
Explicação
Methotrexate inhibits dihydrofolate reductase, preventing regeneration of tetrahydrofolate needed for thymidine synthesis and causing megaloblastic anemia. Folate deficiency elevates homocysteine but not methylmalonic acid, which distinguishes it from vitamin ... Ver explicação completa e trilha adaptativa →