TNFSF18 and narcolepsy: TNFSF8/TNFSF15 and TNFSF13 loci are also associated with the risk of IgA nephropathy, while TNFSF4/TNFSF18 locus has previously been associated with the risk of eczema, asthma and narcolepsy, all with concordant effects to IgA levels (Fig. 2c and Supplemental Table 5).