Pulmonary light chain deposition disease: report of five cases and review of the literature.

Light chain deposition disease (LCDD) in the lung is a rare occurrence. We describe 5 new cases of this entity, review the literature, and compare pulmonary light chain deposits to pulmonary amyloidosis. In addition, we identified 17 patients with pulmonary LCDD in the literature with sufficient clinical information to allow evaluation of clinical presentation, laboratory findings, histologic appearance, and disease progression. In these 22 patients, 2 different histologic patterns were appreciated: diffuse and nodular. A parallel with the diffuse and nodular forms of pulmonary amyloidosis is suggested. The 10 patients with nodular LCDD had an overall better prognosis compared with the 12 patients with diffuse pulmonary LCDD. However, when compared to what is reported in the literature for nodular pulmonary amyloidosis, the patients with nodular LCDD had a higher incidence of an associated lymphoproliferative and/or plasma cell dyscrasia and renal failure. Light chain deposits in the lung are histologically similar to amyloid but are not Congophilic. Their electron microscopic appearance is distinctly different with fibrils in amyloid and granular deposits in LCDD. As the diffuse forms of LCDD and amyloidosis have a similarly poor prognosis, differentiating the 2 entities is probably not critical. However, when present as nodules, LCDD is more frequently associated with an underlying plasma cell dyscrasia or renal failure than is amyloidosis, and therefore the distinction may be clinically important.