Pulmonary amyloidosis: ultrastructural study of early alveolar septal deposits.

A 65-year-old man had tracheobronchial amyloid deposits with osseous metaplasia and amyloid tumors in the lungs, associated with systemic secondary amyloid. Focal alveolar involvement was demonstrated by light microscopy, whereas early deposits, not visible optically, were detected by electron microscopy as focal widening of the basal membrane. The relationship of tracheobronchial amyloidosis to tracheobronchopathia osteoplastica and the similarities between the early pulmonary deposits and those of kidney and thyroid are briefly discussed.