Over the years, patients with recurrent infections and hypogammaglobulinemia generally have been classified as having common variable immune deficiency (CVID), without knowledge of the exact immune pathway defect. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a recently described protein that acts as a barrier to T-cell activation and is an important immune modulator.1-5 The loss of this protein in mice causes fatal autoimmune disease.4 Several investigators observed that CTLA-4 operates as an early checkpoint blockade of T-cell response to antigens and that this regulation is critical for prevention of autoimmunity.1-5 The presence of CTLA-4 averts immune targeting of host tissues, whereas a deficiency results in autoimmunity.2-5 Herein, we describe a patient with CVID who was later identified as having CTLA-4 deficiency and visually disabling autoimmune choroiditis that responded to abatacept, a CTLA-4 analogue. The requirement for approval of the study was waived by the Wills Eye Hospital Institutional Review Board, and the patient provided written consent to allow her data to be used in research.