IPLab:Lab 11:Chagas Disease

Clinical Summary

This 12-year-old boy, whose family had recently emigrated from Brazil, presented to the emergency room with a three-day history of malaise, fever, anorexia, and edema of the face and upper extremities. On physical examination the patient had generalized lymphadenopathy and hepatosplenomegaly. The patient was tachycardic and dysgenic with signs of congestive heart failure. A cardiac biopsy was performed which revealed an active myocarditis with leishmanial forms of parasitic organisms within cardiac myocytes. Close examination of peripheral blood smears revealed occasional circulating trypomastigotes. A complement fixation test for antibodies to Trypanosoma cruzi was strongly positive.

Images

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  This peripheral blood smear from the patient shows two trypomastigotes of Trypanosoma cruzi.

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  This peripheral blood smear from the patient shows a higher power view of a Trypanosoma cruzi trypomastigote. Note the prominent kinetoplast (arrow).

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  This is a low-power photomicrograph of an H & E stained section from the heart biopsy of this patient. Note the organisms within a myocyte (arrow) and the adjacent inflammatory response.

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  This is a higher-power photomicrograph of an H & E stained heart biopsy from this patient. Again, note the organisms within a myocyte (arrow) and the inflammatory response.

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  This is a higher-power photomicrograph of an H & E stained heart biopsy from this patient. At this magnification the organisms within a myocyte (arrows) and the adjacent inflammatory response are more clearly seen. The individual organisms within the myocyte are called amastigotes.

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  This is a higher-power photomicrograph of an H & E stained heart biopsy from this patient. Note the T. cruzi amastigotes (arrows) within this longitudinal section of a myocyte.

Study Questions

• How is Chagas’ disease transmitted?

Reduviid bugs (kissing bugs) bite people while they sleep. The bug defecates on the skin and the infected bug feces is rubbed into the wound. Organisms from the infected feces can also enter the body via mucous membranes. These organisms then circulate via the blood stream to infect cells.

• This patient had acute Chagas' disease. What would you expect to see in a patient with chronic Chagas' disease?

Chronic Chagas' disease leads to congestive heart failure. These patients commonly have right bundle branch block and/or other arrhythmias. These hearts are dilated and hypertrophied, have areas of fibrosis especially in the apex, and often contain mural thrombi. The myocardium is infiltrated with lymphocytes and macrophages and there is interstitial edema and fibrosis. This inflammatory reaction is most severe around the area of the right bundle branch. Patients may also develop megaesophagus and/or megacolon.

Additional Resources

Reference

• eMedicine Medical Library: Chagas Disease (American Trypanosomiasis)
• eMedicine Medical Library: Trypanosomiasis
• Merck Manual: Chagas Disease
• Merck Manual: African Trypanosomiasis