Background: Vitamin D is a vital hormone in preserving calcium and phosphorus homeostasis in the body and maintaining normal growth and mineralization of bones. Case Presentation: We identified a patient with vitamin D dependent rickets type 1A (VDDR1A). This patient had rachitic skeletal manifestations, macrocephaly, retarded motor development, hypocalcemia, hypophosphatemia, markedly elevated alkaline phosphatase, and secondary hyperparathyroidism associated with normal 25 hydroxyvitamin D [25(OH)D] and low 1,25-dihydroxyvitamin D [1,25(OH)2D]. These biochemical abnormalities are consistent with the diagnosis of VDDR1A. Molecular analysis of CYP27B1 gene revealed novel homozygous mutation "Gly125Arg". Unaffected parents were heterozygous carriers. Conclusion: It is highly suggestive that "Gly125Arg" is the molecular defect causing this disease in our patient. Gly125Arg is likely to be a pathogenic mutation that leads to VDDR1A.

Keywords: CYP27B1 gene, Dependent rickets, 1,25 dihydroxyvitamin D, 25 hydroxyvitamine D, Vitamin D, case report