A 9-year-old girl has an indurated area of erythema and swelling just lateral to her left eye, accompanied by posterior cervical lymphadenopathy. She has unilateral painless edema of the palpebrae and periocular tissues.

These findings are followed two days later by malaise, fever, anorexia, and edema of the face and lower extremities.

On physical examination a week later there is hepatosplenomegaly and generalized lymphadenopathy. She then goes into severe congestive heart failure.

Her 32-year-old father also has congestive heart failure, with pedal edema and ascites. If an EKG were performed on him, it would show a right bundle-branch block, or possibly atrioventricular block, premature ventricular contractions, or tachy- and bradyarrhythmias. He suffers a cerebrovascular accident and recovers with minimal loss of function of his right upper extremity. He later develops dysphagia, odynophagia, chest pain, and regurgitation, complicated by aspiration pneumonitis. He develops abdominal pain and constipation.

Question 5.1 - What are the possible infectious causes for these findings?

A myocarditis is likely. In this specific setting, and with this history, viral infection is much less likely than...

Question 5.2 - Where do you think this family lives? What are their living conditions like?

In rural endemic areas 20 to 75% of the population may be affected. An increasing number of cases are found in the United States as patients migrate from endemic areas. Although only about 1% of infected individuals have an acute illness, which may include acute myocarditis, upwards of one-third develop chronic myocardial damage many years later.

Question 5.3 - How is the diagnosis of the child's acute disease made?

The diagnosis of acute Chagas' disease requires the detection of parasites. Microscopic examination of fresh anticoagulated blood or of the buffy coat is the simplest way to see the motile organisms. Parasites also can be seen in Giemsa-stained thin and thick blood smears.

Question 5.4 - How is the diagnosis of the father's chronic disease made?

The diagnosis of chronic Chagas' disease is made by the detection of antibodies that bind to T. cruzi antigens. Demonstration of the parasite is not of primary importance. Several highly sensitive serologic tests for antibodies to T. cruzi are used widely in Latin America, including ELISAs.

However, a persistent problem with these conventional assays is the occurrence of false-positive reactions, typically with sera from patients who have other parasitic infections or autoimmune diseases. For this reason, it is generally recommended that positivity in one assay be confirmed by two other tests and that well-characterized positive and negative comparison sera be included in each run.

Question 5.5 - Describe the cardiac findings.

An acute myocarditis rarely occurs. Most deaths in acute Chagas' disease are due to heart failure. The acute symptoms resolve spontaneously in virtually all patients, who then enter the asymptomatic or indeterminate phase of chronic T. cruzi infection.

Symptomatic chronic Chagas' disease becomes apparent years or even decades after the initial infection. The chronic form is characterized by dilatation of several cardiac chambers, fibrosis and thinning of the ventricular wall, aneurysm formation (especially at the left ventricular apex), and mural thrombi. Chronic progressive heart failure is the rule and is associated with poor survival.

Question 5.6 - What antibiotic regimen is indicated?

Benznidazole if acute. Nifurtimox has also been employed. Patients with congestive heart failure can benefit from the typical diuretic and digitalgic drugs and angiotensin-converting enzyme (ACE) inhibitors.