Localized pleural microdeposition of type A amyloid in a patient with rheumatoid pleuritis. Histologic distinction from pleural involvement in systemic amyloidosis.

Decorticated pleural tissue from a 74-year-old man with rheumatoid arthritis, an exudative pleural effusion, and normal left ventricular function contained microscopic deposits of amyloid A protein, localized to the interface between a deep layer of dense fibrocollagen and a layer of granulation tissue beneath a surface fibrin exudate. Previously reported instances of pleural amyloid deposition have occurred in patients with presumed systemic amyloidosis, and most such effusions are the result of congestive heart failure. This patient had no evidence of systemic amyloidosis, and this case appeared to be an example of an unusual form of localized amyloidosis, so-called periinflammatory amyloidosis A. These observations suggest that amyloid in a pleural biopsy should not be construed per se to be diagnostic of systemic amyloidosis.