The T385M STAT1 gain-of-function mutation confers the most severe disease outcomes

Robert Torrance¹Alexander J. McKenna¹Catherine King²Joe McDowell¹Eleanor O'Callaghan¹Jesmeen Maimaris^1,2Adriana Albuquerque¹Rachel Pearce³Emma Catherine Morris^1,2,4Siobhan Oisin Burns^1,2*

• ¹University College London Institute of Immunity and Transplantation, London, United Kingdom
• ²Royal Free London NHS Foundation Trust, London, United Kingdom
• ³King's College London, London, United Kingdom
• ⁴Department of Haematology, University College London Hospitals NHS Foundation Trust, London, United Kingdom

Background: Gain-of-function (GOF) mutations in STAT1 cause a combined immunodeficiency characterised by chronic mucocutaneous candidiasis (CMC), recurrent infections, and autoimmunity. Mutations in the DNA-binding domain (DBD) have previously been associated with poor outcomes, but the contributions of specific variants to clinical phenotype remain unexplored. Methods: We performed a systematic literature review to identify patients with confirmed STAT1 GOF mutations, integrating new cases with a previously reported international cohort. Clinical and genetic data were analysed at both domain and mutation level to define genotype-phenotype correlations. Results: A total of 533 unique patients from 36 countries were identified, harbouring 135 distinct mutations. As previously reported, DBD mutations were associated with increased risk of systemic infections, bronchiectasis, autoimmunity, and reduced survival. However, mutation-level stratification revealed that the T385M variant accounted for much of this effect. Compared with both other DBD mutations and mutations elsewhere in STAT1, T385M conferred significantly higher rates of infection, bronchiectasis, autoimmunity, and premature death (p < 0.001). Conversely, certain coiled-coil (CC) domain mutations, such as R274Q, were associated with milder disease and improved survival. Conclusion: Our findings demonstrate that the adverse prognosis previously ascribed to DBD mutations in STAT1 GOF is predominantly driven by the T385M variant. Mutation-specific, rather than domain-level, stratification is therefore essential for accurate risk assessment and clinical management. In particular, patients predicted to have severe disease, such as those with the T385M mutation should be considered early for curative interventional therapies such as stem cell transplant or gene therapy.