Background
Leptospirosis is a potentially fatal zoonosis. It can cause a wide range of symptoms, including diffuse alveolar haemorrhage which occurs in a minority of cases but carries a mortality of over 70%. These patients may present with severe acute respiratory failure. The differential diagnosis for diffuse alveolar haemorrhage is broad whereas prompt diagnosis and treatment can be lifesaving.

Case presentation
A 20-year-old previously fit and well trout farm worker presented with a 3-day history of malaise, fevers, diarrhoea, vomiting and jaundice. He developed haemoptysis, severe headaches, neck stiffness and photophobia on the day of emergency admission. He was anaemic and thrombocytopenic. Anuric acute kidney injury (urea 32, creat 507) required immediate haemofiltration. In view of progressive respiratory failure with four-quadrant lung infiltrates on imaging, he was given broad spectrum antibiotics and pulsed methylprednisolone empirically, in case of a vasculitic pulmonary-renal presentation. He was intubated within 48 h of admission. Despite attempted protective ventilatory management, he remained hypoxaemic and developed pneumomediastinum. He was retrieved to a specialist cardiorespiratory intensive care unit on femoro-femoral mobile VV-ECMO. Three days from admission, results showed positive Leptospira IgM and real-time PCR. Serial bronchoscopies showed old and fresh clots, but not the classical progressive late red tinge of the returned lavage fluid. After eight days, VV-ECMO was weaned, he was extubated three days later, and made a full recovery. At 9 months follow-up, he was clinically better, with resolution of the CT scan findings and near normal lung function, albeit with low normal gas transfer.

Conclusions
Leptospirosis is a rare but important differential to be considered in diffuse alveolar haemorrhage presenting to the ICU, especially in young males. A thorough history for occupational or recreational risk factors may offer the diagnostic clue. Most patients recover fully with antibiotics. However, resulting acute severe respiratory failure can ensue. In this situation, early consideration for respiratory ECMO support offers time for clearance of endobronchial clot, parenchymal recovery, and prevention of ventilator-induced lung injury. Steroids have no clear evidence but may be used to avoid delay in treating suspected vasculitic or autoimmune causes of diffuse alveolar haemorrhage.