A full-term, male patient was born in the United Kingdom to parents of Hazars ethnic background, weighing 3.5 kg (50th percentile) and regaining his birth weight by Day 12. There was no significant family history, and he had two healthy siblings. He presented to hospital at 5 weeks of age with fever, respiratory distress, tachypnea, and a C-reactive protein level of 59 mg/L (reference range,, 5 mg/L). During the next 6 months, he had a persistent cough and three further admissions. Chest radiographs showed persistent perihilar changes; he received multiple courses of