Congenital athymia is a life-limiting disorder due to rare inborn errors of immunity causing impaired thymus organogenesis or abnormal thymic stromal cell development and function. Athymic infants have a T-lymphocyte-negative, B-lymphocyte-positive, natural killer cell-positive immunophenotype with profound T-lymphocyte deficiency and are susceptible to severe infections and autoimmunity. Patients variably display syndromic features. Expanding access to newborn screening for severe combined immunodeficiency and T lymphocytopenia and broad genetic testing, including next-generation sequencing technologies, increasingly facilitate their timely identification. The recommended first-line treatment is allogeneic thymus transplantation, which is a specialized procedure available in Europe and the United States. Outcomes for athymic patients are best with early diagnosis and thymus transplantation before the development of infectious and inflammatory complications. These guidelines on behalf of the European Society for Immunodeficiencies provide a comprehensive review for clinicians who manage patients with inborn thymic stromal cell defects; they offer clinical practice recommendations focused on the diagnosis, investigation, risk stratification, and management of congenital athymia with the aim of improving patient outcomes.

Department of Immunology and Gene Therapy Great Ormond Street Hospital for Children NHS Foundation Trust London United Kingdom

Department of Immunology and Gene Therapy Great Ormond Street Hospital for Children NHS Foundation Trust London United Kingdom; Infection Immunity and Inflammation Research and Teaching Department University College London Great Ormond Street Institute of Child Health London United Kingdom

Department of Paediatrics and Institute of Developmental and Regenerative Medicine University of Oxford Oxford United Kingdom; Department of Clinical Immunology Oxford University Hospitals NHS Foundation Trust Oxford United Kingdom

Department of Paediatrics and Institute of Developmental and Regenerative Medicine University of Oxford Oxford United Kingdom; Paediatric Immunology Department of Biomedicine University of Basel and University Children's Hospital Basel Basel Switzerland; Department of Biosystems Science and Engineering ETH Zurich Basel Switzerland

Department of Pediatrics Institute of Clinical Sciences The Sahlgrenska Academy University of Gothenburg Gothenburg Sweden; Department of Rheumatology and Inflammation Research Institute of Medicine The Sahlgrenska Academy University of Gothenburg Gothenburg Sweden

Department of Pediatrics Pediatric Stem Cell Transplantation Program Willem Alexander Children's Hospital Leiden The Netherlands; Department of Immunology Leiden University Medical Center Leiden The Netherlands

Institute of Immunology and Immunotherapy Medical School University of Birmingham Birmingham United Kingdom

San Raffaele Telethon Institute for Gene Therapy IRCCS San Raffaele Hospital Milan Italy; Istituto di Ricerca Genetica e Biomedica Consiglio Nazionale Delle Ricerche Milan Italy

Translational and Clinical Research Institute Newcastle University Newcastle upon Tyne United Kingdom; Paediatric Stem Cell Transplant Unit Great North Children's Hospital Newcastle upon Tyne United Kingdom

Translational and Clinical Research Institute Newcastle University Newcastle upon Tyne United Kingdom; Paediatric Stem Cell Transplant Unit Great North Children's Hospital Newcastle upon Tyne United Kingdom; Department of Paediatric Immunology Children's Health Ireland at Crumlin Crumlin Ireland

References provided by Crossref.org