ESPE Abstracts

The CYP27B1 gene encodes 25-hydroxyvitamin D-1α-hydroxylase. Mutations of this gene cause vitamin D-dependent rickets type 1A (VDDR-IA, OMIM 264700), which is a rare autosomal recessive disorder. Herein we report five patients with 1α-hydroxylase deficiencies. We studied six patients from three families who diagnosed as 1α-hydroxylase deficiency clinically. All patients had hypocalcemia, hypophosphatemia, hyperphosphatasemia, elevated serum PTH, normal or high vitamin D levels, and low or inappropriately normal calcitriol levels at presentation. Patients were diagnosed less than 18 months years old. All patients had a family history of consanguinity. Homozygous mutations in the CYP27B1 gene were found in all the patients. Four of them have splice donor site mutation in intron 1 (c.195+2 T>G), causing partial retention of the intron and a shift in the reading frame. Clinically, all the patients required calcium and calcitriol initially and then continuously calcitriol treatment. Autosomal recessive diseases are common in countries where the consanguineous marriages are common. VDDR-IA should be kept in mind patients with vitamin D resistant rickets.