Homocystinuria due to CBS (cystathionine beta-synthase) deficiency causes elevated plasma homocysteine and methionine. Which clinical feature is NOT typically seen in CBS-deficient homocystinuria?
- A Elevated urinary orotic acid and megaloblastic anemia ✓
- B Ectopia lentis (downward lens dislocation)
- C Thromboembolism due to endothelial damage
- D Marfanoid habitus with tall stature
Explanation
Classic CBS-deficient homocystinuria presents with ectopia lentis (characteristically DOWNWARD, contrasting with Marfan's upward lens dislocation), thromboembolism (homocysteine damages endothelium, activating coagulation), Marfanoid habitus, osteoporosis, and intellectual disability. Elevated orotic acid and megaloblastic anemia are features of urea cycle disorders (orotic acid) and folate/B12 deficiency (megaloblastic anemia). While B6-non-responsive homocystinuria does not cause orotic aciduria. Treatment: B6 (pyridoxine, CBS cofactor PLP) for responsive cases, betaine, methionine restriction, folate.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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