Calcium and Parathyroid USMLE Step 1 Practice Question
A 7-year-old boy presents with muscle cramps, paresthesias, and positive Chvostek sign. Vital signs show HR 102 bpm, BP 118/76 mmHg, RR 18, temp 37°C, SpO2 98%. Serum calcium is 6.8 mg/dL (normal 8.5-10.5), phosphate 6.2 mg/dL (normal 2.5-4.5), PTH 312 pg/mL (normal 15-65), and magnesium 2.1 mg/dL (normal 1.7-2.2). Serum creatinine is normal. He denies recent neck surgery or radiation. Which of the following is the most likely diagnosis?
Answer choices
- AAutosomal dominant hypocalcemia
- BPseudohypoparathyroidism type Ia
- CNutritional rickets from vitamin D deficiency
- DVitamin D-dependent rickets type 2
- EVitamin D-dependent rickets type 1Correct answer
- FHypoparathyroidism secondary to magnesium depletion
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