FAS and Down syndrome: Autoimmune cytopenias coexisting with clinical features of organ-specific or systemic immunodysregulatory phenotype in pediatric patients with CVID and genetically defined IEIs, such as STAT3 GOF (signal transducer and activator of transcription 3 gain-of-function) disease, APDS [activated PI3Kδ (phosphoinositide-3-kinase delta) syndrome], FAS-ALPS (autoimmune lymphoproliferative syndrome), and Kabuki syndrome, have also been recently reported (36).