Lung involvement as diffuse alveolar-septal amyloidosis occurs in most cases of systemic primary amyloidosis. Involvement limited to the lungs, and lung involvement by secondary amyloidosis, are both very rare. Diffuse alveolar-septal amyloidosis produces bilateral reticulonodular interstitial infiltrates that may be mistaken for pulmonary fibrosis radiographically. Patients may die of progressive respiratory insufficiency. Grossly, the lungs are bulky and the cut surfaces have a diffuse rubber-sponge appearance and texture. Histologically, the lung architecture is generally preserved with thickening of alveolar septa by amorphous eosinophilic amyloid diffusely or as multiple interstitial nodules.