Vitamin D-Dependent Rickets Type II

To the Editor: We reported previously on a 22-year-old woman with hypocalcemia, secondary hyperparathyroidism, osteomalacia, osteitis fibrosa cystica, and marked elevation of serum 1,25-dihydroxyvitamin D.¹ We termed this disorder vitamin D–dependent rickets Type II and have attributed the findings to impaired endorgan response to 1,25-dihydroxyvitamin D. Since that time several additional cases have been reported,^{2 , 3} including those of a brother and sister in whom the onset of the disease occurred in early childhood.³ The hypocalcemia and secondary hyperparathyroidism in our patient were corrected with vitamin D3, 4000 units per day for four weeks, but we were unable to.