This approach has highlighted how both loss-of-function and gain-of-function alleles of STAT1 (a key transcription factor involved in IFN signalling and susceptibility to mycobacterial and viral infection) may perturb normal immune function, leading to clear disease phenotypes [17], in this case, chronic mucocutaneous candidiasis (CMC), a persistent or recurrent infection with Candida albicans involving the nails, skin, oral, or genital mucosa [23]. Here, IFNA1 is linked to chronic mucocutaneous candidiasis.