Respiratory failure and multiple fractures in vitamin D-dependent rickets

A 20-month-old boy presented with multiple fractures and respiratory failure. He was found to have vitamin D-dependent rickets. The rickets did not improve with phosphate, calcium and calciferol. The rickets healed, however, with large doses of 1-alpha-hydroxycholecalciferol. The presentation is unusual and the response to therapy suggests metabolic heterogeneity in vitamin D-dependent rickets.