Q. A 35-year-old woman comes to the emergency department because of fever and productive cough. The patient has medical history significant for non-alcoholic fatty liver disease. For the last year, the patient has had multiple attacks of pneumonia that eventually led to bronchiectasis. She was a former smoker (she smoked 10 cigarettes per day since the age of 30). Vital signs show blood pressure: 130/90 mmHg, heart rate: 100 bpm, temperature: 39.2 degrees Celsius, respiratory rate: 25 bpm. The patient is admitted for further evaluation. Laboratory analysis reveals a deficiency of all immunoglobulin subclasses. Which of the following is the most likely diagnosis?