Cerebrovascular involvement in systemic AA and AL amyloidosis: a clear haematogenic pattern

Amyloid deposits in cerebral vessels are common in beta-amyloid diseases (A lzheimer's disease, congophilic amyloid angiopathy, Down's syndrome and her editary cerebral amyloidosis with haemorrhage of the Dutch type). We report of 20 autopsies on patients who had died with systemic amyloidosis of the AA, A lambda and AK types: the brains were examined for the occurrence of a myloid. Vascular amyloid was detected in choroid plexus (in 17 of 20 cases) , infundibulum (5 of 8), area postrema (6 of 11), pineal body (3 of 7) and subfornical organ (2 of 3), but not in cortical and leptomeningeal vessels. Immunohistochemical classification of the cerebral amyloid and the systemi c amyloid syndrome showed identity proving the same origin of both. The dis tribution is indicative of a haematogenic pattern of amyloid deposition in systemic amyloidosis and is different from that in Alzheimer's, prion, ATTR and cystatin C diseases. It corresponds to areas of the brain with a "leak y" blood-brain barrier. Additionally, all the cases with AA amyloidosis exh ibited an A beta coreactivity in choroid plexus vessels. In one exceptional case, A beta reactivity of AA amyloid also occurred outside of the brain.