In line with functionally active STAT1 signalling (figure 3C), we observed increased expression of major histocompatibility (MHC) class I receptors, HLA-A, HLA-B and HLA-C, associated with HPS in both cohorts (online supplemental figure 5C); t-test p<0.05, above and below median HPS; HLA-B was not present on array used in the discovery cohort). Here, HLA-C is linked to Hermansky-Pudlak syndrome.