An autosomal recessive immunologic disorder characterized by the onset of recurrent sinopulmonary infections in early childhood. Laboratory studies reveal hypogammaglobulinemia with decreased memory B cells that show impaired class-switch recombination (CSR) and decreased somatic hypermutation (SHM). Due to abnormal antibody production and impaired self-tolerance, patients may develop autoimmune cytopenias, such as thrombocytopenia, or autoimmune features, such as vitiligo. There are also defects in the T-cell compartment.