A 7-year-old boy with a restrictive diet avoiding fruits and vegetables presents with gum bleeding, perifollicular hemorrhages, and delayed wound healing. Vital signs: BP 95/60, HR 102, RR 20, Temp 37°C, SpO2 98%. Laboratory studies show serum ascorbic acid 0.1 mg/dL (normal 0.6-2.0). Gingival examination reveals petechiae without loose teeth. Deficiency of which of the following most directly impairs collagen cross-linking required for normal scar formation?
- A)Vitamin K dependent gamma carboxylation of clotting factors
- B)Vitamin C dependent hydroxylation of proline and lysine residuesGABARITO
- C)Biotin dependent carboxylation of pyruvate
- D)Folate dependent thymidylate synthesis
- E)Copper dependent lysyl oxidase activity
Explicação
Vitamin C is required for hydroxylation of proline and lysine residues during collagen synthesis. Deficiency causes scurvy, which presents with bleeding gums and defective wound healing because poorly hydroxylated collagen lacks normal tensile strength. Ver explicação completa e trilha adaptativa →