Germline STAT1 LOF mutations with MSMD (Mendelian susceptibility to mycobacterial disease) and STAT1 GOF mutations with CMC (chronic mucocutaneous candidiasis) were first reported in 2001 and 2011, respectively; since then, research has confirmed that both STAT1-GOF and LOF germline mutations cause immunodeficiency and immune dysregulation, with a wide clinical spectrum beyond malignancies (4–6). The gene discussed is STAT1; the disease is Chronic mucocutaneous candidosis.