Aim Тo assess the frequency of low vitamin D deficiency and conduct an association search for genetic variants (c.1206T>C, c.152T>C, c.1174+283G>A) of the VDR gene with clinical manifestations, calcidiol levels and response to therapy in cystic fibrosis ( CF), bronchial asthma (BA), juvenile idiopathic arthritis (JIA).

Material and Method 283 patients with CF, 160 with BA, 150 with JIA and 333 healthy children in the control group were examined, and calcidiol content was determined. Testing of polymorphic variants of the VDR gene (c.1206T>C, c.1175–9G>T, c.152T>C, c.1174+283G>A) was carried out using PCR and RFLP analysis.

Results For CF liver cirrhosis with portal hypertension is more often (OR=4.300; p=0.051) realized in carriers of the AA genotype BsmlI of the VDR gene. Children with genotypes TT FokI polymorphism and AA BsmlI polymorphism VDR gene do not respond to vitamin D supplementation. The occurrence of manifestations of the ‘atopic march’ increases many times when carrying the genotype TT TaqI (OR=13.000; p=0.046), genotypes AA and GA BsmlI (OR= 18.000; p=0.017). Calcidiol deficiency against the background of asthma is 2.7 times (p = 0.003) more often recorded among carriers of the TT and CT genotypes TaqI of the VDR gene. Patients with the AA genotype BsmlI polymorphism of the VDR gene do not respond to vitamin D supplementation. The risk of systemic onset of JIA, polyarticular variant, high degree of activity, uveitis, high frequency of biological therapy (p <0.05) are carriers of the TT genotype TaqI, TT genotype C FokI, genotype AA BsmlI of the VDR gene. Рatients with genotypes CC TaqI, TT FokI, AA BsmlI polymorphism VDR gene do not respond to vitamin D supplementation.

Conclusions The high frequency of low vitamin D supply and the contribution of VDR gene polymorphisms during the studied diseases and the formation of vitamin D supply are shown.