—  SPECIALTY CONFERENCE  —

PEDIATRIC PATHOLOGY

Case 3 - Acute Chagas' myocarditis (trypanosomiasis cruzi)

David H. Walker, M.D.
University of Texas
Galveston, Texas

Clinical history
This previously healthy, developmentally normal, 7 month old male child from south Texas had a febrile illness with coryza three weeks before admission and was treated with antibiotics for otitis media 10 days before admission. He was admitted to the intensive care unit with cough, pulse 146/min, respirations 50/min, temperature 97.4°F, clear lungs, and hepatosplenomegaly. Admission laboratory data included WBC 22,200/_l, hemoglobin 9.2 g/dl, serum sodium 125 mMol/l, and pO2 76 mmHg. Chest radiographs showed cardiomegaly and increased pulmonary vascular markings, ECHO showed pericardial effusion and decreased myocardial contractility, and EKG showed accelerated junctional rhythm.

Treatment included multiple antibiotics, pericardiocentesis, and creation of a pericardial window. The hospital course was characterized by progressive cardiac failure and death.

Slides  (Click to enlarge)


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Acute Chagas' disease with intense myocardial inflammation (x50). Acute Trypanosoma cruzi myocarditis contains a severe mononuclear cell infiltrate (x50). Acute chagasic myocarditis with three cardiac myocytes filled with amastigote stage Trypanosoma cruzi (x100). Acute chagasic myocarditis with a cardiac myocytes containing Trypanosoma cruzi with identifiable round nuclei and rod-shaped kinetoplasts (x250).

Differential diagnosis

  1. Acute Chagas' myocarditis
  2. Viral myocarditis
  3. Idiopathic mycocarditis

Diagnosis Acute Chagas' myocarditis (trypanosomiasis cruzi)

Discussion
Trypanosoma cruzi is endemic in Central and South America with 16-18 million infected persons and 100 million persons living in conditions at risk of infection. Persons become infected by the deposition of trypanosome-contaminated feces by infested triatomid bugs and its subsequent autoinoculation into the dermis or onto mucous membranes (e.g., the conjunctiva, where inflammation may be recognized as Romaña sign). Other modes of infection include infected blood transfusions and mother-to-fetus. Trypanosoma cruzi is maintained in natural cycles involving more than 100 species of wild and domestic mammals including opossums, dogs, wood rats, armadillos, raccoons, and cats from the southern US to central Argentina. Infected animals maintain lifelong parasitemia, an enormous reservoir of the agent. Mainly known as a chronic infection, Chagas' disease can cause a lethal disease, particularly in infants and young childern, ususally owing to acute myocarditis and more rarely meningoencephalitis. There have been five patients with autochthonous Chagas' disease diagnosed in the US, four of whom were children ages 2-3 weeks to 18 months.

The definitive diagnosis of American trypanosomiasis is made by identifying the protozoal parasites. Highly motile circulating trypomastigotes can frequently be detected in a wet preparation of anticoagulated blood or buffy coat or in a Giemsa-stained smear. In immunocompromised patients including those with AIDS, the diagnosis of acute Chagas' disease may be facilitated by microscopic examination of bone marrow, lymph node aspirate, CSF, or pericardial fluid. Cultivation in special liquid medium or xenodiagnosis, although not widely available and requiring weeks to complete, are more sensitive than microscopy. Polymerase chain reaction detection of trypanosomal DNA is highly sensitive and specific if performed properly. The present case was confirmed by specific PCR of two gene targets of T. cruzi. In the most recently reported case in an 18 month old child, T. cruzi was identified in two different laboratories by PCR of three gene targets. This definitive diagnosis led to early, curative treatment with benznidazole. The diagnosis was considered only because of the mother's pursuit of the identification of an engorged, infected adult female Triatoma sanguisuga found in the baby's bed. The child never developed antibodies to T. cruzi. Serologic surveys have demonstrated that low percentages of persons in southern states of the US have antibodies reactive with T. cruzi. However, lack of availability and standardization of the serologic assays are drawbacks to their routine use in diagnosing Chagas' disease.

References

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