A 14-year-old boy referred for suspected Marfan syndrome is tall with long limbs, pectus excavatum, high-arched palate, and joint laxity. He has inferior displacement of the lens. Urine homocysteine is markedly elevated. Which feature distinguishes his condition from Marfan syndrome?
- A Downward lens dislocation, intellectual disability and venous thrombosis ✓
- B Upward and temporal lens dislocation with aortic root dilatation
- C Absence of skeletal involvement despite ocular findings
- D Autosomal dominant inheritance with normal intelligence
Correct answer: A. Downward lens dislocation, intellectual disability and venous thrombosis
Explanation
Homocystinuria due to cystathionine beta-synthase deficiency mimics Marfan habitus but shows downward and inward lens subluxation, intellectual disability, osteoporosis, malar flush and a marked thromboembolic tendency. In Marfan the lens dislocates upward and temporally, intelligence is normal, and aortic root dilatation dominates the prognosis. Elevated homocysteine with reduced cystathionine beta-synthase activity confirms the diagnosis.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.