A 23-month-old Sudanese girl had failure to thrive and an unusual gait. She was noted to be a happy, developmentally appropriate child (Figure, A) with bowed legs (Figure, B), thick wrists (Figure, C), and dental caries. Her weight (8.7 kg) and height (72.5 cm) were below the third percentiles for her age. Her diet consisted predominantly of breastfeeding 5 times daily; however, she did consume 500 mL of juice, 4 teaspoons of rice, and a few bites of a sandwich most days. Her medical history included iron-deficiency anemia that was corrected with oral iron supplementation. She was receiving no other medications. The patient was born in the United States after an unremarkable prenatal, delivery, and postnatal course. She resided in the northeastern United States with her parents. Laboratory studies revealed an elevated total alkaline phosphatase level (1151 U/L) and an elevated intact parathyroid hormone level (16.2 pmol/L [reference range, 1.6-6.8 pmol/L]). The 25-hydroxyvitamin D level was decreased (19 nmol/L [reference range, 25-137 nmol/L). The complete blood cell count, remainder of the comprehensive metabolic profile, ionized calcium level, and phosphorous level were unremarkable. Plain radiographs of the patient's knees (Figure, D) and wrists (Figure, E) demonstrated osseous changes including metaphyseal cupping and flaring, epiphyseal irregularities, and widening of the physeal plates. A chest radiograph was unremarkable.