Acute Chagas' Disease

The characteristic pathological process is the chagoma. This can be a primary lesion at the site of inoculation or a secondary lesion with the same pathogenesis. The principal and most important findings are in the heart and central nervous system.

In the heart, a multifocal myocarditis is invariably present and is more intense than other types of myocarditis. The heart is flabby and enlarged, with dilatation being a more predominant feature than hypertrophy, often accompanied by thinning of the ventricular walls (Fig. 4.5A& B). Focal areas of inflammation and hemorrhage may occur in the endocardium (rarely leading to mural thrombosis) and in the epicardium, giving rise to pericardial effusion. Microscopically, there is a severe diffuse interstitial and interfibrillary edema, congestion, and numerous swollen myofibers containing leishmania (Fig. 4.5C). There is degeneration of the myofibers and infiltration by lymphocytes, plasma cells and other mononuclear cells, (Fig. 4.5D). In addition, there is hyaline necrosis of isolated cardiac fibers and some fibers have dark bars of clumped fibrils arranged tranversely on their longitudinal axis. This change, seen in sections stained with iron hematoxylin or in silver impregnated sections (the "Magarinos-Torres' lesion"), is characteristic and perhaps specific for acute Chagas' myocarditis. The cardiac valves are not involved.

In patients with encephalitis or meningoencephalitis, examination of the brain, spinal cord and meninges may show similar inflammatory infiltrates with mononuclear cells, congestion, perivascular inflammation, small hemorrhages, and neuronophagia. Chagas described these parasitic nodules in the cerebrum, cerebellum, basal nuclei, pons, and spinal cord. The parasites may be present within the reticulum cells of the meninges as well as in the glial cells and neurons. Lesions may be found elsewhere in the body, such as the liver, spleen, prostate, and testes, but parasites are rare and must be diligently searched for, sometimes at great length.

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Fig. 4.5 Acute Chagas' myocarditis. (A) Large flabby heart with dilatation being more predominant than hypertrophy. (B) Same heart opened, showing thinning of the left ventricular wall with severe necrosis of myocardial tissue. (C) Hematoxylin-eosin stained section of the same myocardium showing inflammation and edema. (D) Acute Chagas' myocarditis in a child from Brazil. Myofibers are degenerating and widely separated by the inflamed and edematous interstitium. Amastigotes, which cluster in the degenerating myofibers, cannot be discerned in photographs C and D. H & E x 115. AFIP 62-5540.