Monthy Case Studies - 1999
Case #11 - May, 1999
An adult man, an immigrant from El Salvador, went to the Emergency Room of a U.S. hospital with fever and confusion that did not respond to antibiotic treatment. A CT scan showed a brain lesion. The patient was HIV-positive and his last visit to El Salvador was one year earlier. A spinal tap showed low glucose and high protein levels in the CSF. In addition, the organisms shown in Figures A through D were found in the CSF (size approximately 20 micrometers; Giemsa stain). What is your diagnosis? Based on what criteria? What other diagnostic tests would you suggest?
Answer to Case #11
This was a case of American trypanosomiasis caused by Trypanosoma cruzi. The stages shown were trypomastigotes, identifieable by the kinetoplast (K, red arrows, Figure A below) that was located posteriorly to the nucleus (N, blue arrows). Other recognizable elements included the anteriorly placed flagellum (Fla, green arrows) and the undulating membrane (UM, black arrow). The species identification as T. cruzi was based on the large size of the kinetoplast, which bulged in the posterior half of the body. The diagnosis of T. cruzi is also compatible with the clinical history: the patient is from Central America, and in HIV-positive individuals, invasion of the central nervous system (possibly due to a reactivation of chronic Chagas disease) has been described. In Latin America, another trypanosome, T. rangeli, can also be found in humans, but T. rangeli is larger (average 30 micrometers long compared to 20 micrometers in T. cruzi), has a small kinetoplast (different from the prominent kinetoplast of T. cruzi), and causes infections that are asymptomatic.
Additional diagnostic procedures in this patient included examination of the Giemsa stained buffy coat of the blood (negative); culture of blood and CSF (negative); and immunofluorescence assay for antibodies to T. cruzi in the CSF (negative) and the serum (positive at 1:128).
Two public health notes: a) when handling specimens from patients with suspect Chagas disease, observe blood safety precautions because the parasites are infective and the infection is difficult to treat; b) the occurrence of T. cruzi is an important problem in ensuring the safety of the blood supply in the Americas.
More on: American Trypanosomiasis
Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.