In Reply.—Several lines of evidence have recently indicated the defective 1α-hydroxylase system in X-linked hypophosphatemia. Thus, the rational therapeutic approach is to use 1,25-dihydroxyvitamin D together with phosphate supplementations. In certain patients, the therapeutic response has been very dramatic, especially in growth velocity indexes, as noted in our article. However, other patients fail to gain in height despite such therapy. Using the Z score of linear growth, we were unable to show significant differences in linear growth due to the heterogeneity of the therapeutic response. There are other effects and complications of the use of 1,25-dihydroxyvitamin D that our group and others are working on, and we still hope to convince Dr Stickler to use 1,25-dihydroxyvitamin D and phosphate supplementation in the not-too-distant future.