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Clinical Characteristics

Acute Chagas' disease may occur at any age, but is most frequent in the first years of life, especially during the summer. It has been estimated that, in the initial stage of infection (first 2 months), only 1% of those infected will develop recognizable clinical signs; therefore the vast majority of infections go undiagnosed. In previous years, the mortality during this stage was felt to approximate 50% in some areas, but currently is less than 5% in most areas and, when subclinical cases are considered, the overall mortality falls below 1%. Less than 5% of patients will present in the acute phase with meningoencephalitis or heart failure, both of which indicate a bad prognosis. The mortality rate from acute myocarditis or meningoencephalitis varies from 2-10%. In Laranja's series of 235 acute patients, the mortality was 9.4% with death from congestive heart failure, convulsive seizures, or secondary infection.

The incubation period of acute Chagas' disease varies from 1 to 2 weeks depending on the portal of entry, size of inoculum, and the patient's age. Clinical signs include a high continuous fever up to 104°F, which may persist for one or more months, malaise, muscle pains, sweating, anorexia, vomiting, and diarrhea.

In about 50% of patients the trypanosomes enter through the conjunctiva, causing elastic edema of the upper and lower eyelids, chemosis of the conjunctiva, and enlargement of the preauricular lymph nodes (Romaña's sign) (Fig. 4.6). In 25% of patients a portal of entry can be identified by a nodular or ulcerative skin lesion (chagoma) at the site of inoculation with accompanying regional lymph node enlargement. The presence of Romana's sign and/or a chagoma is quite helpful in the clinical diagnosis of acute Chagas' disease; these signs may disappear within 30 days. The lymphadenitis, which at first is localized to the area of the primary lesion, later becomes generalized. A firm non-pitting edema may develop in the legs and feet and become generalized; this is probably related to hypoproteinemia and usually disappears in about 3 weeks. The liver and spleen frequently enlarge after several weeks. Parasitic induced lesions in the lungs may result in pneumonia from secondary infection. Symptoms of meningoencephalitis may be the primary manifestation of Chagas' disease, but are more frequently noted after onset of other clinical signs.

Fig. 4.6 Child with Romana's sign: unilateral conjunctivitis, palpebral and periorbital edema and preauricular lymphadenopathy. AFIP 62-3934-6.

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