IRF4 and infectious disease: Although we did not find any IRF4 mutations in a pilot cohort of 25 patients with sporadic WD, these and other patients may also develop WD due to other inborn errors of immunity, possibly related to IRF4, as suggested by the apparent genetic heterogeneity and physiological homogeneity underlying severe infectious diseases (Andersen et al., 2015; Casanova, 2015a; Casanova, 2015b; Ciancanelli et al., 2015; Israel et al., 2017; Lamborn et al., 2017; Ogunjimi et al., 2017; Vanhollebeke et al., 2006; Zhang et al., 2018; Zhang et al., 2015).