Novel primary immunodeficiency disorders are being identified with next generation sequencing technologies. We describe 1 patient with cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) haploinsufficiency who had recurrent enhancing brain lesions, nodular pulmonary infiltrates, hepatosplenomegaly, immune cytopenias, as well as progressive hypogammaglobulinemia and lymphopenia. We describe a second patient with activated p110δ syndrome (APDS)/p110δ activating mutation causing senescent T cells, lymphadenopathy, and immunodeficiency (PASLI) in association with recurrent respiratory tract infections, Epstein-Barr virus infection, lymphadenopathy, elevated serum IgM, and progressive lymphopenia. These presentations highlight the need for astute clinical judgment in the evaluation of patients with potential primary immunodeficiency disorders.