A 26-year-old woman with stable Crohn's disease was admitted with a 4-day history of dyspnoea and haemoptysis. She required an FiO2 of 0.5 to maintain arterial saturation at 93% (94–98) with a normal PCO2. Investigations:* haemoglobin 88 g/L (115–165) MCV 90 fL (80–96) white cell count 10.0 × 109/L (4.0–11.0) platelet count 522 × 109/L (150–400) ESR 102 mm/1st h (<20) INR 1.2 serum creatinine 67 µmol/L (60–110) serum albumin 36 g/L (37–49) serum CRP 290 mg/L (<10) CT scan of chest see image