Fig. 1.

Chest radiograph from a 5-month-old infant with severe combined immunodeficiency showing bilateral patchy shadowing secondary to interstitial pnuemonitis due to infection with respiratory syncytial virus and Pneumocystis jiroveci. There is hyperinflation of the lungs, and the midline pleural borders of the upper lobes are visible because the thymic shadow is absent (courtesy of The Paediatric Immunology Unit, Great North Children’s Hospital, Newcastle upon Tyne)