Letter to the Editor regarding: Epistatic effects in pathophysiology of asthma and the “missing heritability” of this disease

We are probably only at the beginning of the road leading to explanation of how some genetic variants can cause chronic disease. It seemed that the so-called “genome-wide association studies” (GWAS) would clarify this issue. Takahiro Yoshikawa et al., however, at the outset of their recent paper wrote that “most of these studies have only managed to explain a small additional percentage of hereditability estimates” [1]. These researchers are convinced that the mechanisms of genetic conditioning of chronic diseases will be explained more effectively by so-called “epistatic analyses” [1]. They remember that, contrary to Mendel’s classical law of heredity in which each gene locus exerts an independent effect on a single phenotype, it has been proven that 2 different gene loci can affect the same phenotype and that the action between 2 loci is classically defined as ‘epistasis’ [1].