Hereditary hypophosphatemic rickets represented by
X-linked hypophosphatemic rickets (XLH) is a rare disorder characterized by
hypophosphatemia, elevated
alkaline phosphatase (ALP) and undermineralization of bone. Active
vitamin D and
phosphate are administered to correct
hypophosphatemia and elevation of ALP. Overtreatment with
phosphate leads to
secondary hyperparathyroidism, and a large dose of active
vitamin D has a risk of
hypercalciuria. To understand the situation concerning treatment of patients with
hereditary hypophosphatemic rickets in Japan, we conducted a questionnaire survey of pediatric endocrinologists. Answers were obtained from 53 out of 68 hospitals where the pediatric endocrinologists worked. One hundred and thirty-five patients were treated in 28 hospitals during November 2009 and May 2010; 126 patients suffered from
hereditary hypophosphatemic rickets, and 9 had
hypophosphatemia caused by other miscellaneous reasons. The distribution of patient age was as follows: 27 (21%) were between 6 mo and 6 yr of age, 39 (31%) were between 6 and 12 yr of age, and 60 (48%) were more than 12 yr of age. Active
vitamin D was given to 123 patients, and
phosphate was given to 106 patients. As for the dose of
phosphorus, 37.2-58.1 mg/kg/d was given divided into 2 to 6 aliquots. There were various control targets of treatment, including serum
phosphate, serum ALP, rachitic change, urinary Ca/Cr,
parathyroid hormone and growth. It is very important to avoid side effects of these treatments. No evidence is available about the optimal dose of
phosphate or number of administrations in the treatment of patients with
hypophosphatemic rickets. Although there is a recommendation for clinical management of patients with
hypophosphatemic rickets, we should set a clinical guideline for it in Japan.