Co-deposition of amyloidogenic immunoglobulin light and heavy chains in localized pulmonary amyloidosis

Localized pulmonary amyloidosis is a rare condition whose pathogenesis is insufficiently understood. In the present study, we report a case of localized pulmonary amyloidosis associated with lung-restricted lymphoplasmacytoid lymphoma, monoclonal for immunoglobulin (Ig) G lambda (λ). Biochemical microtechniques have been applied for extraction, purification, and characterization of amyloid proteins. Surprisingly, chemical analysis of these proteins revealed a not-previously-described case of combined deposits containing Ig fragments of gamma heavy chain (variable domain) and λ light chain (constant domain). In view of the absence of circulating monoclonal Ig, this case supports the hypothesis that localized amyloid is formed by local plasmacytoid cells.