[Vitamin D poisoning in infants: a preventable cause of hypercalciuria and nephrocalcinosis]

The established prophylaxis for vitamin D-deficient rickets today is 400 IU vitamin D3 given daily during the first year of life. With this regimen, vitamin D intoxication is a rare event. Nevertheless, we have recently seen 4 infants with vitamin D intoxication after a so called "stoss" prophylaxis, i.e. twice 300,000 units (7.5 mg) vitamin D3 orally within 4 weeks. One patient presented with failure to thrive due to marked hypercalcemia (3.9 mmol/l) and nephrocalcinosis, 2 patients showed medullary nephrocalcinosis on ultrasonography and one patient had gross hematuria and spontaneous passage of a calculus. Three patients had massive hypercalciuria (calcium/creatinine ratio 1.8-4.8 mol/mol, normal less than 1). The 25 (OH) vitamin D3 plasma levels, measured only in 2 patients, were strikingly increased (270 and 158 nmol/l, respectively, normal 25-80). Urinary calcium excretion slowly decreased to normal values on a low calcium diet and high fluid intake. Nephrocalcinosis, however, persisted in 2 patients and showed a slight progression ultrasonographically in one patient. The short time interval between vitamin D administration and onset of symptoms and the subsequent clinical course provide strong evidence that hypercalciuria and nephrocalcinosis were due to vitamin D "stoss" prophylaxis in all four cases. In conclusion, there is no indication for vitamin D "stoss" prophylaxis for vitamin D-deficient rickets in infants. Vitamin D intoxication still has to be considered as a possible cause of hypercalciuria.