Immunohistochemical identification of the AA protein in lattice dystrophy

We examined the amyloid deposits of lattice dystrophy type I for common components of primary and secondary amyloid using the sensitive unlabelled antibody peroxidase-antiperoxidase technique. Tissue sections of formalin-fixed, paraffin-embedded specimens from three patients with lattice dystrophy were reacted with antisera specific for free immunoglobulin light chains, prealbumin, amyloid A (AA) protein, and amyloid P (AP) protein. The lattice amyloid was positive for the AA protein associated with secondary amyloid. The deposits were also stained with the protein AP antiserum in each case. We were unable to detect the presence of immunoglobulin light chains associated with primary amyloid or prealbumin associated with another heredofamilial form of amyloid. Sera from two patients with lattice dystrophy were tested for the presence of the serum amyloid A related protein, the apparent precursor of AA amyloid, by immunoelectrophoresis and immunodiffusion. The sera showed no reaction with the AA antiserum with these techniques. Lattice amyloid differed from secondary systemic amyloid in the reaction with potassium permanganate. Congo red staining of lattice deposits was not abolished by treatment with potassium permanganate. Our findings suggest that the amyloid proteins in lattice dystrophy are antigenically similar to those of secondary amyloid and the hereditary form associated with familial Mediterranean fever.