Leptospirosis is a worldwide zoonosis affecting wild and domestic mammals. It is most commonly transmitted to humans by indirect contact with infected animals. Vascular injury, mainly capillary damage, and hemorrhagic diathesis are prominent features in the affected organs. The most severe form of the disease presents with high fever, intense jaundice, hemorrhagic diathesis, hepatic and renal dysfunction, mental status changes, and cardiovascular collapse. Focal or diffuse areas containing alveoli filled with erythrocytes characterize the pulmonary involvement. These latter conditions, although unusual, are associated with significant mortality.