Calcium and Parathyroid USMLE Step 1 Practice Question
A 7-year-old boy presents with tetany and a generalized seizure. Vital signs show HR 110/min, RR 22/min, BP 95/60 mmHg. ECG demonstrates prolonged QT interval. Serum calcium is 6.2 mg/dL, phosphate 6.1 mg/dL, and PTH 18 pg/mL. He has distinctive facial features including micrognathia and a fish-shaped mouth, short stature, and normal intelligence testing. No cardiac murmurs are appreciated. Which chromosomal abnormality best explains these findings?
Answer choices
- ATurner syndrome (45,X)
- BTrisomy 21
- CWilliams syndrome (7q11.23 deletion)
- D22q11 deletion (DiGeorge syndrome)Correct answer
- EKlinefelter syndrome (47,XXY)
- F5p deletion (Cri-du-chat syndrome)
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