Abstract 155: Vitamin D dependent rickets type II: Our experience and systematic review

Background: Hereditary vitamin D resistant rickets, is a rare autosomal recessive disease caused by variants affecting VDR gene. We aimed to describe our experience and systematically review the world literature. Objective: To evaluate the phenotypic and genotypic spectrum of VDDR2. Methods: The clinical and genetic spectrum of VDDR2 were analyzed. Results: Six patients of VDDR 2 were included. The mean age at the development of rachitic changes was 12±3.79 months. Baseline biochemistry revealed hypocalcemia (6.67±1.5 mg/dl), hypophosphatemia (3±1.5 mg/dl) with elevated serum alkaline phosphatase (3579±845 IU/ml) and PTH (372±183 pg/ml). Three novels variants in VDR gene were detected (p.N444D=1, p.I268T=1, p.H85R=1, p.H355TfsTer7=1). A systematic review (probands 112) revealed alopecia in majority of patients (81.2%). Complete response to oral therapy with supra-physiological dose of calcitriol and high dose of oral calcium was observed in 32.5% of cases. Recurrent variants specific to geographical locations were p.Lys45Glu (Africa); p.Cys41Tyr, p.Gln152Ter (Asia); p.Gln356Ter (Europe); p.Gln259Glu (Latino). Patients with variants in ligand binding domain (LBD) had better response to oral therapy compared to cases with DBD variants. Conclusion: Patients with VDDR2 presents in infancy with alopecia. Higher complete response rate to oral therapy can be anticipated in cases with variants affecting LBD.