Histological and histochemical changes of the skeletal muscle in human chronic Chagas' disease

Trypanosomiasis

African (sleeping sickness) and American (Chagas' disease) trypanosomiasis, caused by protozoa of the family Trypanosomatidae, are diseases that are endemic in parts of Africa and Latin America, respectively. Physicians in developed countries may occasionally see cases because of extensive travel and immigration from endemic countries. Although neurological involvement is common in both, its incidence and clinical presentation differ considerably. African trypanosomiasis, caused by subspecies of Trypanosoma brucei (T b rhodesiense, T b gambiense), is transmitted by the tsetse fly and causes meningoencephalitis, in which somnolence is a prominent feature. Parasites may reach the brain parenchyma through the choroid plexus or the Virchow Robin spaces. American trypanosomiasis, caused by Trypanosoma cruzi is transmitted by reduviid bugs. While lesions in the central nervous system are not prominent, except in the reactivated forms which occur in immunodeficient patients, the peripheral nerve, mainly the autonomic nervous system, is frequently involved, leading to the cardiomegaly and the digestive megaviscera. Congenital infections may also occur. In this paper we give an account of the epidemiology, clinical presentation and pathological features of these two protozoal infections based on human and experimental studies of both the central and peripheral nervous system.

Exercise Performance and Skeletal Muscles in Patients With Advanced Chagas Disease

STUDY OBJECTIVE

This study was designed to evaluate the peripheral muscle metabolic and structural characteristics in patients with advanced Chagas disease (ChD), and whether they were related with exercise performance.

DESIGN

Cross-sectional study.

SETTING

Outpatient cardiomyopathy clinic of a university hospital.

PATIENTS AND METHODS

We studied 11 stage II patients, 8 stage III patients, and 11 healthy volunteers. All patients underwent exercise testing and peripheral muscle biopsies. The muscles were also studied in control subjects. Muscle biopsy specimens were analyzed for histochemical characteristics. In six patients, the muscle was studied ultrastructurally.

RESULTS

The data demonstrate more glycolytic and less oxidative capacity of the peripheral muscle in patients with advanced ChD (increased proportion of type IIb fibers, increased proportion of fibers with low nicotinamide adenine dinucleotide diaphorase activity, high proportion of darkly stained fibers for alpha-glycerophosphate dehydrogenase activity, and lower levels of citrate synthase). Many capillaries in patients with ChD had an abnormal aspect: they were either closed or showed a thicker wall. The ultrastructural study also showed fiber atrophy and abnormal capillaries even in patients with normal functional capacity. Some muscle characteristics (enzyme activity, mean cross-sectional area of the fiber, and capillarity) related with exercise parameters (anaerobic threshold, and peak oxygen pulse).

CONCLUSIONS

These findings indicate that patients with advanced ChD have decreased oxidative capacity and a shift to anaerobic metabolism in the skeletal muscle. They also suggest that muscular abnormalities are related to oxygen delivery, which is probably reduced in part by the abnormal muscle microvasculature. Those changes could affect oxygen extraction, and therefore exercise tolerance in these patients.

[Chronic nervous form of Chagas disease: clinical course and anatomopathology of a case followed-up for 20 years]

The chronic nervous forms of Chagas' disease involve both the central and peripheral nervous systems although they are not detected at the frequency indicated by Chagas in his initial observations. The present report concerns a patient with chronic Chagas' disease since childhood who progressively developed involvement of voluntary motility, muscle tone, coordination, and cranial nerves. The patient also had Chagas' heart and colon disease. The patient died after surgery for hemicolectomy and was autopsied. Histologic study of the central nervous system revealed demyelination of the spinocerebellar tracts and posterior columns, a great reduction in the Purkinje cells number, extensive cell loss of the substantia nigra and locus coeruleus, lacunar state in the basal nuclei, tissue infiltration by aberrant Herring bodies, porencephaly, and thickening of the meninges.

[Peripheral denervation in the various clinical forms of Chagas' disease]

EMG examination was performed in 41 patients with Chagas' disease, belonging to the several clinical forms of the disease. Constant and direct relationship between the amount of muscle skeletal denervation and the clinical forms has been shown. In addition light peripheral axonal neuropathy was seen. Both muscular and sensory denervation was intense in the group with cardio-digestive form, moderate in the groups with either cardiac or digestive form and light in the group with the indeterminate form. The severity of the clinical symptoms was not related with the amount of peripheral denervation.

The neuromuscular pathology of experimental Chagas' disease

In this work, we describe skeletal muscle, neuromuscular junction, nerve and spinal cord lesions in the mouse model system of Chagas' disease. Myositis was a common finding and Trypanosoma cruzi amastigote nests were frequently found in the muscle fibers. Angular atrophy, targetoid fibers, groups of atrophic fibers, fibrosis, myofiber necrosis and phagocytosis of cellular debris were also observed. The neuromuscular junction studies showed degeneration of intramuscular nerve fibers, swelling and distortion of nerve endings and multiple ramifications on the same muscle fiber. Collateral, terminal and ultraterminal axonal sprouts were also present. Inflammatory neuropathy was seen in all of the infected mice. Demyelination, axonal degeneration, remyelination and axonal regeneration were observed in the transverse sections. There was an average reduction of 29% in the total number of myelin fibers. The teasing of single myelin fibers showed segmental and paranodal demyelination and remyelination more frequently than axonal degeneration and regeneration. The lumbar spinal cords presented inflammatory cell infiltration associated with tissue destruction. Amastigote nests were found in 3 out of the 8 infected mice studied. There was a mean loss of 21% of the large cytoneurons of the anterior horn of the lumbar spinal cord.

Neuropathy associated with experimental Chagas' disease

Mice were acutely and chronically infected with Trypanosoma cruzi and then examined histologically for the presence of lesions in the peripheral nervous system. In acutely infected animals, small lymphocytic and macrophagic infiltrates were found in the nerves in association with intracellular parasites. Little or no nerve damage was present at this stage. In chronically infected animals, large perivascular granulomatous infiltrates were found in association with multifocal, predominantly demyelinative lesions of neighboring nerve fibers. Similar inflammatory infiltrates were present in muscles and were frequently associated with vasculitis and destruction of muscle fibers. Our pathological findings and the negative results produced by intraneural injections of sera from chronically infected animals and the positive results following injections of small numbers of live trypanosomes suggest that the demyelination is not due to circulating serum factors such as antibodies cross-reacting with peripheral myelin. Delayed-type hypersensitivity may be induced by the presence of the parasites, a notion supported by the development of granulomas in naive mice injected intravenously with helper T cells from chronically infected animals.

Inhibition of muscle differentiation by trypanosoma cruzi

L6E9 rat myoblasts were infected in tissue culture with the myotropic Brazil strain of Trypanosoma cruzi. The effect of parasite infection on the ability of myoblasts to differentiate into myotubes was studied. Both morphological and biochemical differentiation were found to be profoundly affected by parasitic infection in a dose-related fashion. Evidence is presented to suggest that infected myoblasts can no longer differentiate. Differentiation, once underway, seemed unaffected by the parasitic infection; biochemical markers of differentiation remained intact.

Electromyographical findings in human chronic Chagas' disease

An electromyographical investigation of 80 patients with chronic Chagas' disease was made. It was found that 79% of the studied patients had EMG manifestations of old and chronic denervation of the upper and lower limbs without clinical features of nervous system involvement.