Type I Vitamin D Dependent Rickets

ABSTRACT

PURPOSE: Vitamin D dependent rickets (VDDR) is a rare, autosomal recessively transmitted disorder characterized by hypocalcemia, hypophosphatemia, increased alkaline phosphatase, secondary hyperparathyroidism and many other clinical features. Type l VDDR arises from primary deficiency in the renal 1alpha-hydroxylase that produces 1,25 (OH)2D3. So patients with type I VDDR require life long administration of vitamin D. METHODS: There had been 6 children (4 boys and 2 girls) who were diagnosed as type I VDDR in the Department of Pediatrics, Seoul National University Children's Hospital from March 1983 to May 1997. The medical records, Clinical findings, laboratory, radiologic findings, and response to therapy of these children were analyzed retrospectively. RESULTS: The median age at diagnosis was 19.5 month, and 2 families (33.3%) had family history of rickets. The major presenting symptoms were bowing leg (100%), short stature (100%), and hypocalcemic tetany (67%). Serum levels of 1,25 (OH)2D3 7.0 3.06pg/mL (normal 20-76pg/mL), respectively. Pretreatment serum levels of calcium (6.9 1.67mg/mL), phosphate (6.9 1.67mg/mL) and alkaline phosphatase (1892 966.4IU/L) were returned to normal levels after treatment (P<0.01). The height standard deviation scores (Z scores) were increased significantly, also (P<0.01). The side effects detected during vitamin D ttherapy were hypercalcemia (33%), hypercalciuria (67%) and nephrocalcinosis (50%). CONCLUSION: This is the first report of type I VDDR in our country. All patients revealed the characteristic clinical, laboratory and radiologic findings, and one third of patients had positive family history. The treatment improved all the clinical, laboratory and radiologic findings significantly including growth. However, complications developed in some patients during the long- term therapy of vitamin D.