Lymphatic amyloidosis, a previously unrecognized form of amyloid deposition in generalized amyloidosis

Although amyloid deposition in relation to blood vessels is a well-recognized feature of generalized amyloidosis, lymphatic vessel amyloidosis is not mentioned in the literature. Systematic investigation of tissue removed at autopsy from patients with generalized amyloidosis and biopsy specimens from cases of localized amyloidosis and familial Mediterranean fever showed that amyloid deposition around lymphatics is by no means uncommon. The material investigated was mainly large and small bowel, lung, heart and kidney. Amyloid was identified by green birefringence with the Congo red stain on cross-polarization and lymphatics by their lack of immunostaining for CD34. Involvement of lymphatics was noted in 20 of the 42 organs from which specimens were examined, and was always accompanied by involvement of blood vessels and/or the interstitium. In the intestine, lymphatic amyloidosis was found mainly in the submucosa and subserosa, and was also demonstrated by electronmicroscopy in one case. Although lymphatic amyloidosis was equally common in the heart, lung and kidney, it was usually less prominent here than in the intestine. No lymphatic involvement was seen in localized amyloidosis. As the lymphatics play a central role in the resorption of interstitial proteins, they are probably also involved in the resorption of amyloid proteins. Amyloid deposition in the vicinity of lymphatics is probably the result of decompensation of this process.