A 9-year-old girl born of nonconsanguineous parents presents with a history of recurrent generalized tonic-clonic seizures since age 7 months, uncontrolled with 3 antiepileptic agents. The mother reports that the child has stunted growth and decreased cognitive function compared with other children her age. Physical examination is remarkable for short stature, round face, positive Chvostek sign, brachydactyly, and absence of outer 2 knuckles (fourth and fifth digits) on making a fist. Remainder of the physical examination results are unremarkable. Laboratory studies reveal total serum calcium level of 6.3 mg/dL (reference range, 8.7-10.2 mg/dL); serum phosphorous, 6.9 mg/dL (reference range, 2.5-4.3 mg/dL); alkaline phosphatase, 126 U/L (reference range, 33-96 U/L); and serum albumin, 4.2 g/dL (reference range, 3.5-5.5 g/dL). Twenty-four hour urinary calcium–creatinine ratio is 0.10. Thyroid-stimulating hormone is 65.18 mIU/L (reference range, 0.34-4.25 mIU/L), with a free thyroxine level of 0.54 μg/dL (reference range, 5.4-11.7 μg/dL). Concentrations of serum cortisol and insulinlike growth factor 1 are within reference range for the age and sex of the patient. Bilateral hand x-ray shows shortened fourth and fifth metacarpals (Figure).