Vitamin D receptor ApaI a allele is associated with better childhood asthma control and improvement in ability for daily activities.

Vitamin D levels have been suggested as a marker of disease severity in asthmatic children. Our aim was to investigate possible associations between the vitamin D receptor (VDR) FokI, BsmI, ApaI, and TaqI polymorphisms and asthma susceptibility and control in children. 127 Greek children with asthma and 91 healthy controls were genotyped for VDR FokI, BsmI ApaI, and TaqI polymorphisms using Sequenom MassARRAY iPLEX platform. Asthma control was assessed according to the Global Initiative for Asthma guidelines (GINA) and Childhood Asthma Control Test (C-ACT) and, for the first time, tested for its possible association with VDR SNPs. Asthmatic children were grouped as "controlled (n=49)", "partially controlled (n=38)," and "uncontrolled (n=40)," according to GINA classification. No association was found between VDR polymorphisms and asthma prevalence. Asthmatic children with the VDR ApaI aa genotype had significantly higher C-ACT score compared with asthmatic children carrying the AA/AC VDR ApaI genotypes (p=0.011). The frequency of VDR ApaI aa genotype was significantly higher in controlled asthma group (n=92) than uncontrolled asthma group (n=35), according to C-ACT (24.5% vs 0.0%, p<0.001) and GINA (32.7% vs 7.5%, p=0.001). Also, VDR ApaI aa genotype was negatively associated with limitation in daily activities because of asthma (p=0.004). VDR ApaI aa genotype was positively associated with well-controlled asthma according to GINA and C-ACT questionnaire and negatively associated with decreased limitation in daily activities in asthmatic children, further supporting the importance of Vitamin D pathway in asthma.