Lin et al. found that intronic variants can impact alternative splicing by interfering with splice site recognition that 5′-splice sites of exon 20 in the IKBKAP gene causes skipping of exon 20, resulting in malfunction of IKBKAP in 99.5% of familial dysautonomia (FD) cases [29]. The gene discussed is ELP1; the disease is Familial dysautonomia.