A 22-month-old African American boy born at 38 weeks by normal vaginal delivery presents to a local hospital from a private pediatric office for failure to thrive. He was seen by his pediatrician until aged 1 month but was lost to follow-up. His delay in walking prompted his mother to reestablish care at age 22 months.
History of illness
There were no reported complications during pregnancy or delivery. According to his mother, the toddler has always been small and has had slow growth, but he has never lost weight. He was exclusively breastfed until aged 18 months, and his current diet consists of 1 cup of whole milk and several cups of fruit juice per day, grains, meats, and minimal fruits and vegetables. He lives with his mother and 3-year-old sister in public housing. His mother has a history of iron deficiency anemia and sickle cell trait. His maternal grandmother has lupus and rheumatoid arthritis. His sister is reportedly healthy and has appropriate growth and development.
On admission, the patient is notably small for his age and is below the first percentile for weight, height, and head circumference. He is alert and cooperative, and is babbling during the exam. His anterior fontanelle is open and his oropharynx and dentition are normal. No abnormalities are discovered during a cardiopulmonary exam. There are nodules along his rib cage. His abdominal exam is normal and reveals no hepatosplenomegaly or masses. He has bowing deformities of both arms and legs, wide wrists, and mild diffuse hypotonia. Based on a physical exam and history of developmental milestones, he has both gross motor and fine motor delay.
Laboratory and imaging tests
The patient’s blood chemistry panel is presented in Table 1. His urinalysis has 1+ protein (reference range, negative) and is otherwise normal.
A radiograph is obtained at presentation (Figure 1). Because of the findings on imaging, further testing is performed with results as follows: 25-hydroxyvitamin D (25[OH]D), 13 ng/mL (reference range, 30-100 ng/mL); phosphorus, 2.99 mg/dL (reference range, 4.37-6.59 mg/dL); magnesium, 3.1 mg/dL (reference range, 1.7-2.3 mg/dL); and parathyroid, 88 pg/mL (reference range, 14-72 pg/mL).