Review Question - QID 5247

A mother brings her 4-year-old daughter to your clinic for evaluation of knocked knees and short stature. On exam, the patient ambulates with a circumduction gait pattern and frequently falls. Plain radiographs are displayed in Figure A. Laboratory data is obtained and notable for calcium 9.1 mg/dL (RR 8.5-10.2 mg/dL), phosphorus 2.9 mg/dL (RR 4.3-5.4 mg/dL), alkaline phosphatase 405 U/L (RR 169-372 U/L), 25-OH vitamin D 38 ng/mL (RR 25-50 ng/mL), 1,25-OH vitamin D 21 pg/mL (RR 24-86 pg/mL), PTH 25 pg/mL (RR 15-65 pg/mL). The child is adopted and family history is not known. Which is the most likely diagnosis?