Electron Microscope Appearances of a Fibrin-staining Component in an Aschoff Nodule from Acute Rheumatic Fever

Abstract

ELECTRON microscope investigations of ‘fibrinoid’ in Aschoff nodules from biopsy specimens of the left atrial appendage in mitral stenosis have shown that collagen fibrils are intimately related to the abnormal material and appear to take part in its formation¹. In these specimens the ‘fibrinoid’ did not stain positively for fibrin. The abnormal material was periodic acid–Schiff positive and usually stained with the collagen stains. In a few cases of acute rheumatic fever a fibrin-staining component is recognized, and this is found especially in early reticular Aschoff bodies, structures described by Klinge² as the early rheumatic ‘Fruhinfiltrat’. Death from acute rheumatic fever is extremely rare and it is virtually impossible to obtain fresh specimens for electron microscope studies. The only source of material is paraffin embedded and an attempt has been made to see if useful information could be obtained by utilizing tissue already fixed and embedded.