CASE PRESENTATION: In April 2014, a 24-year-old man went to hospital for a physical examination. He had not experienced orthopnoea and palpitation. He had no record of pulmonary diseases and rheumatic heart disease. Physical examination showed no pallor, icterus, cyanosis, clubbing, lymphadenopathy, oedema of the feet and raised jugular venous pulse. There was marked reduction in movement of the left hemithorax and evident left chest deformity, and the shift of the trachea and heart to the left. The entire left hemithorax, except the infraclavicular area, was dull on percussion. Breath sound was almost absent on the left side. A three-dimensional image of the lungs reconstructed from the CT scan showed that right lung herniated across to the left side resulting in a horseshoe shape, and the destroyed left lung (Figure).