Filaggrin gene mutations and new SNPs in asthmatic patients: a cross-sectional study in a Spanish population

BACKGROUND Several null-mutations in the FLG gene that produce a decrease or absence of filaggrin in the skin and predispose to atopic dermatitis and ichthyosis vulgaris have been described. The relationship with asthma is less clear and may be due to the influence of atopy in patients with associated asthma. METHODS Four hundred individuals were included, 300 patients diagnosed with asthma divided into two groups according to their phenotype (allergic and non-allergic asthma) and 100 strictly characterized controls. The coding region and flanking regions of the FLG gene were amplified by PCR. We proceeded to the characterization of potential gene variants in that region by RFLP and sequencing and analysed their association with lung function parameters, asthma control and severity, and quality of life. RESULTS We identified two null-mutations (R501X and 2282del4), seven SNPs previously described in databases and three SNPs that had not been previously described. One of the SNP identified in this study (1741A > T) was more frequently detected in patients with non-allergic asthma, worse FVC, FEV1 and PEF values and a higher treatment step. In addition, lowered spirometric values were observed in the non-allergic group carrying any of the nonsynonymous SNPs. CONCLUSIONS In the association study of genetic variants of the FLG gene in our population the 1741A > T polymorphism seems to be associated with non-allergic asthma.