A patient who presented with dyspnea and suspected interstitial pulmonary fibrosis suffered a fatal pulmonary haemorrhage with no feasible cause for bleeding. Autopsy revealed abundant amyloid deposits in both lungs with a diffuse alveolar septal distribution pattern. Amyloid was also found in the cardiac interstitium and in many vessel walls. Considering the affected organs and the histological characteristics, the deposits were regarded as light chain-type. Amyloidosis, which is generally an uncommon disease, very rarely affects the lung predominantly. Haemorrhagic diathesis is a known complication in amyloidosis patients, although fatal haemorrhage is rare and has not yet been reported solely of pulmonary origin. This report describes an uncommon case of idiopathic systemic amyloidosis mainly manifesting in the lungs. The diagnosis was established after fatal pulmonary haemorrhage caused by vessel impairment due to additional vascular amyloid deposits.