PORTAL AMYLOID - NOVEL AMYLOID DEPOSITS IN GASTROINTESTINAL VEINS

Objective.-To specify uncharacterized amyloid deposits in gastrointest inal vessels of the elderly. Materials and Methods.-The gastrointestin al tracts from 110 consecutive autopsies of individuals aged 85 years and older were examined for amyloid using Congo red staining. Immunohi stochemical classification of the amyloid deposits was conducted using antisera directed against amyloid A, apolipoprotein A-I, apolipoprote in A-II, apolipoprotein B, apolipoprotein C-I, lysozyme, lambda and ka ppa light chain amyloid fibril proteins, transthyretin, beta(2)-microg lobulin, and amyloid P component. Electron microscopic examination ass essed the ultrastructural features. Results.-Thirty-eight (35%) of the 110 cases had gastrointestinal amyloid deposits. In 17 cases the amyl oid fibril proteins were defined immunohistochemically. In five cases (5%) the amyloid could not be classified because amyloid deposits were not present in the deeper serial sections used for immunohistochemist ry. In 13 cases (11%) the vascular amyloid deposits could not be chara cterized because they did not demonstrate immunoreactivity with any of a panel of antibodies specific for the fibril proteins of all major e xtracerebral amyloids. In three individual cases, the vascular amyloid deposits showed variable immunoreactivity, with deposits being negati ve in some vessels. The immunohistochemically nonreactive vascular amy loid in these 16 cases had several consistent features: it affected on ly vessels of the small and large intestine, it was limited to mesente ric veins, it consisted of small dot- or comma-like deposits located i n close proximity to fragmented elastic fibers, and it demonstrated in consistent immunostaining for amyloid P component. Conclusions.-The si milar morphologic characteristics of nonreactive gastrointestinal amyl oid deposits, which we have designated ''portal amyloid,'' suggest a c ommon origin. Determination of whether portal amyloid represents a new type of amyloid will require chemical analysis.