STAT1 and severe combined immunodeficiency: These alternative IEIs, including severe combined immunodeficiency (SCID), chronic granulomatous disease (CGD), X-linked hyper IgM syndrome (HIGM), signal transducer and activator of transcription 1 (STAT1) gain of function (GOF), hyper IgE syndrome (HIGE), and activated phosphoinositide 3-kinase δ syndrome (APDS), have been reported to exhibit BCG complications [51,52].