Abstract
Late onset combined immunodeficiency (LOCID) is a rare variant of common variable immunodeficiency (CVID), typically affecting adult patients who present with opportunistic infections (OI) and/or low CD4+ T lymphocytes. Diagnostic delay is common due to the rareness of this entity, increasing morbidity and mortality. We report on a 66-year-old male who developed a severe gastrointestinal cytomegalovirus (CMV) infection, refractory to antiviral treatment and anti-cytomegalovirus specific human immunoglobulin administration, with a fatal outcome due to an undiagnosed LOCID. LEARNING POINTS: Infections in patients with primary immunodeficiencies (PIDs) could be more severe and life-threatening than in immunocompetent hosts.PIDs are not exclusive to paediatric patients; diagnostic delay is common, and they should also be suspected in adulthood.Diagnostic delay in PID patients is associated with more morbidity and mortality.