Enrichment of Immune Dysregulation Disorders in Adult Patients with Human Inborn Errors of Immunity

Human inborn errors of immunity (IEI) comprise a group of diseases resulting from molecular variants that compromise innate and adaptive immunity. Clinical features of IEI patients are dominated by susceptibility to a spectrum of infectious diseases, as well as autoimmune, autoinflammatory, allergic, and malignant phenotypes that usually appear in childhood, which is when the diagnosis is typically made. However, some IEI patients are identified in adulthood due to symptomatic delay of the disease or other reasons that prevent the request for a molecular study. The application of next-generation sequencing (NGS) as a diagnostic technique has given rise to an ever-increasing identification of IEI-monogenic causes, thus improving the diagnostic yield and facilitating the possibility of personalized treatment. This work was a retrospective study of 173 adults with IEI suspicion that were sequenced between 2005 and 2023. Sanger, targeted gene-panel, and whole exome sequencing were used for molecular diagnosis. Disease-causing variants were identified in 44 of 173 (25.43%) patients. The clinical phenotype of these 44 patients was mostly related to infection susceptibility (63.64%). An enrichment of immune dysregulation diseases was found when cohorts with molecular diagnosis were compared to those without. Immune dysregulation disorders, group 4 from the International Union of Immunological Societies Expert Committee (IUIS), were the most prevalent among these adult patients. Immune dysregulation as a new item in the Jeffrey Model Foundation warning signs for adults significantly increases the sensitivity for the identification of patients with an IEI-producing molecular defect.

Next Generation Sequencing for Detecting Somatic FAS Mutations in Patients With Autoimmune Lymphoproliferative Syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is a primary immune regulatory disorder clinically defined by chronic and benign lymphoproliferation, autoimmunity and an increased risk of lymphoma due to a genetic defect in the FAS-FASL apoptotic pathway. Genetic defects associated with ALPS are germinal and somatic mutations in FAS gene, in addition to germinal mutations in FASLG, FADD, CASP8 and CASP10 genes. The accumulation of CD3+TCRαβ+CD4-CD8- double negative T-cells (DNT) is a hallmark of the disease and 20-25% of ALPS patients show heterozygous somatic mutations restricted to DNT in the FAS gene (ALPS-sFAS patients). Nowadays, somatic mutations in the FAS gene are detected through Sanger sequencing in isolated DNT. In this study, we report an ALPS-sFAS patient fulfilling clinical and laboratory ALPS criteria, who was diagnosed through NGS with a targeted gene panel using DNA from whole blood. Data analysis was carried out with Torrent Suite Software and variant detection was performed by both germinal and somatic variant caller plugin. The somatic variant caller correctly detected other six ALPS-sFAS patients previously diagnosed in the authors’ laboratories. In summary, this approach allows the detection of both germline and somatic mutations related to ALPS by NGS, avoiding the isolation of DNT as the first step. The reads of the somatic variants could be detected even in patients with DNT in the cut off limit. Thus, custom-designed NGS panel testing may be a faster and more reliable method for the diagnosis of new ALPS patients, including those with somatic FAS mutations (ALPS-sFAS).

Autoimmune Lymphoproliferative Syndrome in Children with Nonmalignant Organomegaly, Chronic Immune Cytopenia, and Newly Diagnosed Lymphoma

This study investigated the frequency of and predictive factors for autoimmune lymphoproliferative syndrome (ALPS) in children with lymphoma, chronic immune cytopenia, and nonmalignant organomegaly. Thirty-four children with suspected ALPS (n=13, lymphoma; n=12, immune cytopenia; n=9, nonmalignant organomegaly) were included. Double-negative T-cells, lymphocyte apoptosis, and genetic findings were analyzed. Patients were stratified into two groups as proven/probable ALPS and clinically suspected patients according to the ALPS diagnostic criteria. Of the 34 patients, 18 (53%) were diagnosed with proven/probable ALPS. One patient had a mutation (c.652-2A>C) in the FAS gene. The remaining 16 (47%) patients were defined as clinically suspected patients. Predictive factors for ALPS were anemia and thrombocytopenia in patients with lymphoma, splenomegaly and lymphadenopathy in patients with immune cytopenia, and young age in patients with nonmalignant organomegaly. ALPS may not be rare in certain risk groups. Our study indicates that screening for ALPS may be useful in children having lymphoma with cytopenia at diagnosis, in those having nonmalignant organomegaly with immune cytopenia, and in those having chronic immune thrombocytopenic purpura or autoimmune hemolytic anemia with organomegaly developing during follow-up.