Six novel mutations in 25-hydroxyvitamin D3 1α hydroxylase gene in patients with pseudovitamin D deficiency rickets
Geneviève Abeguilé1,2, Nadia Coudray1,2, Nicolas Richard1,2, Agnes Linglart2,3 & Marie-Laure Kottler1,2
Pseudovitamin D deficiency rickets also called vitamin D-deficiency rickets type 1 (VDDR 1) is an autosomal recessive disorder in which 25-hydroxyvitamin D3 1 alpha-hydroxylase gene (CYP27B1) is deficient. VDDR1 is characterized by hypocalcemia,hypophosphatemia elevated serum PTH levels and low or undetectable serum concentrations of 1,25(OH)2D.
We screened for mutations CYP27B1 in ten individuals from seven unrelated families with VDDR-1. In three families parents were consanguineous. The first symptoms appeared within the first year of life except in F5 et F7 where diagnosis was made in two boys at 8 and 5 years respectively. In these patients laboratory abnormalities were mild with normal serum 1α,25(OH)D3 but elevated serum alkaline phosphatase activity and PTH. Patients responded well to treatment with 1α-OHD.
The nine exons were amplified by PCR and sequenced. We identified eight unclassified variants including six new one which were not found in a panel of normal control.
The classical laboratory criteria for the diagnosis of VDDR1 may fail to identify patients with partial but significant defect in this enzyme and hence, this syndrome may be more common than previously appreciated.