Pulmonary cystic disorder related to light chain deposition disease.

Light chain deposition disease (LCDD) is a rare disorder that very uncommonly affects the lung. We report three cases of severe cystic pulmonary LCDD leading to lung transplantation. Such a presentation has never been previously reported. The three patients present with a progressive obstructive pulmonary pattern associated with numerous cysts diffusely distributed in both lungs. The disease was histologically characterized by non-amyloid amorphous deposits in the alveolar walls, the small airways and the vessels. It was associated with emphysematous-like changes and small airway dilation. Monotypic kappa light chain fixation was demonstrated on the abnormal deposits and along the basement membranes. Electron microscopy revealed coarsely granular electron-dense deposits in the same localizations. Mild extrapulmonary deposits were found in salivary glands in one patient. No immunoproliferative disorder was identified. We conclude that LCDD may primarily affect the lung, present as a pulmonary cystic disorder, and lead to severe respiratory insufficiency.