Coinciding kappa AL amyloidosis and kappa light chain deposition disease in the lung

Excerpt

Amyloid is primarily composed of insoluble extracellular fibrillar protein aggregates arranged in anti-parallel beta pleated sheet secondary structures that appear as amorphous, eosinophilic extracellular deposits when stained with hematoxylin and eosin (H&E) [1, 2]. After Congo red staining, these microscopically appear yellow-green under polarized light [1, 2]. The resulting structure is resistant to protease and able to self-propagate [1, 2]. Accumulation of amyloid in tissues may be localized to an organ, or, in more serious cases, systemic—resulting in physiologic derangements [1, 3]. Monoclonal immunoglobulin light chains produced by B cells or plasma cells are an amyloid precursor protein for amyloid light chain (AL) amyloidosis [2, 3]. Localized AL amyloidosis is most often composed of kappa light chains—compared to lambda AL amyloidosis predominating in systemic forms [3]. In the lung, localized amyloidosis often presents as slow-growing circumscribed nodules, classified as nodular amyloidosis, which may take on cystic features [3]. …