Pulmonary amyloidosis in hematological disorders.

Amyloidosis is defined by tissue deposits of amyloid, a proteic substance with a characteristic spatial structure of beta-sheet fibrils assembled into bundles. This structure results in specific staining with Congo red dye, with green birefringence under polarized light microscope. AL amyloid forms from amyloidogenic immunoglobulins produced by clonal plasma cells. Pulmonary amyloidosis may be either part of systemic amyloidosis (primary amyloidosis or associated with myeloma) or organ-limited. Pulmonary interstitial amyloidosis in systemic amyloidosis is rarely symptomatic unless amyloid deposits severely affect gas exchange alveolar structures, thus resulting in serious respiratory impairment. Localized parenchymal involvement may present as nodular amyloidosis or as amyloid deposits in the vicinity of pulmonary lymphomas. Tracheobronchial amyloidosis, which is not associated with evident clonal proliferation, results in airway stenoses necessitating iterative laser treatment. Treatment of systemic amyloidosis aims at reducing the clonal cell populations producing amyloidogenic immunoglobulins, using high-dose chemotherapy followed by autologous stem cell transplantation in carefully selected patients. Its efficiency in treating diffuse pulmonary amyloidosis has not been established.