Severe vitamin D deficiency: A persistent yet preventable problem among Canadian youth

A 6-month-old Inuit, formula-fed infant was taken to the emergency room by ambulance following a generalized tonic–clonic seizure. On examination, the infant was fussy and hypotonic. Biochemistry was consistent with severe vitamin D deficiency (undetectable 25-hydroxyvitamin D3 and urinary calcium to creatinine ratio, low serum ionized calcium, normal serum phosphate and elevated parathyroid hormone [PTH] and alkaline phosphatase). A hand radiograph showed no signs of rickets. Risk factors for vitamin D deficiency were determined to be severe maternal vitamin D deficiency and absence of infant postnatal vitamin D supplementation. Given the history of a seizure, the infant was treated with intravenous calcium along with oral vitamin D3 4000 IU/day and elemental calcium 50 mg/ kg/day in four divided doses. Once the ionized calcium was >1.0 mmol/L (after 72 hours), the intravenous calcium was discontinued. The patient remained on vitamin D3 4000 IU/day and supplemental calcium until the biochemistry normalized (total duration of high-dose therapy was 5 months). The infant was then transitioned to vitamin D3 800 IU/day as maintenance therapy, calcium supplementation was discontinued and adequate calcium intake was encouraged through dairy products to meet the recommended intake for age (260 mg elemental calcium daily).