Cytochemistry of brain amyloid in adult dementia.

A cytochemical study of 14 cases of adult dementia revealed the presence of gamma globulin in the amyloid of three cases of congophilic angiopathy by means of immunofluorescence microscopy. In these cases, the additional identification of human albumin is regarded to indicate a non-specific macromolecular leak in the blood-brain barrier. Both reactions are inhibited by prior absorption with the appropriate serum protein. Twelve of the 14 cases had congophilic amyloid deposits which were not affected by permanganate pre-treatment, so that immunoglobulin content remains a possibility, despite the negative immune reaction. Alcianophilia was studied at a varying pH and electrolyte concentration, but these findings do not appear to have nosologic significance. The three positive cases are characterized by a rapid terminal decline. The heterogeneity of amyloid and the significance of immunoamyloid in the pathogenesis of adult dementia is discussed.