Background: Primary immunodeficiency (PID) in adults is rare and mostly revealed by infections.
Material and methods: Adults without predisposing factors who were admitted to an intensive care unit (ICU) for infection were screened for PID.
Results: Six PID cases were diagnosed, mostly revealed by encapsulated bacterial infections.
Conclusion: Investigation of PID after ICU discharge should be considered to improve early detection.
Keywords: Adult; Infection; Intensive care unit; Primary immunodeficiency; Secondary immunodeficiency.