Because of the COVID19 pandemic, you are practicing telemedicine. You are shown
the EKG and abdominal film (see below) of a 50-year-old patient whose main complaint
is persistent abdominal bloating and chronic constipation. You are given no other
history nor the results of a physical exam or laboratory tests, and you must rely
on your clinical accumen to make a diagnosis.
What is your diagnosis, what lab test(s) would you order to confirm you suspicions,
and what treatment, if any, do you recommend?
DIAGNOSIS: Chagas' disease (CD). CD is caused by infection with the protozoan Trypanosoma cruzi which is transmitted most often by Triatominate insect vectors (e.g., the Raduvid
"kissing bug"); less frequently, the disease is acquired through blood transfusions,
organ transplants, transplacentally, or by the oral route. Estimates indicate that
between 5 and 18 million persons in South America are currently infected, with a mortality
rate of more than 10,000 deaths annually.
CD has three phases: acute, intermediate, and chronic. The acute phase is usually
asymptomatic but may produce flu-like symptoms such as fever and malaise in up to
5% of cases. The intermediate phase is also typically asymptomatic and more than 50%
of infected persons will remain in this phase for life and never experience long-term
sequellae. After a decade or more, 20-30% of infections will cause cardiovascular
disease (myocarditis, supraventricular or ventricular techycardias, biventricular
block, mural thrombi with potential embolization, congestive heart failure); another
20-30% of infections will cause gastrointestinal disease (megaesophagus, megacolon
with dysphagia, abdominal bloating, chronic constipation or obstipation) due to massive loss of myenteric neurons.
The diagnosis of CD is established by examining Giemsa-stained peripheral blood
smears, by hemoculture, by serological testing (DAT, IFAT-polyvalent, IgM, IgG tests)
and/or by molecular analysis (nested-PCR).
To be effective, treatment of CD must be initiated in the acute or intermediate
phase of the disease; there is little evidence to support efficacy of treatment in
persons with symptomatic cardiovascular or gastrointestinal disease. Available trypanocidial
drugs include benzidazole and nifurtimox. There is increasing interest in developing
trypanosomid selective proteosome inhibitors to treat CD.
In the presented case, the abdominal film shows a markedly dilated bowel (megacolon)
and the EKG shows a supraventricular tachycardia (300 beats/minute) and biventricular
heart block.