Q&A Medicine>>>>>Infectious Diseases
Question 54#

A 32-year-old man complains of fever, diarrhea, and abdominal pain. He has had intermittent fevers for the past month, with episodes of bloody diarrhea. The abdominal pain started 2 weeks ago, and since that time he has had fewer episodes of diarrhea. He denies any jaundice, pale stools, or IV drug use. The patient emigrated from Mexico 6 months ago, and has been living with his extended family in Arizona. On examination, there is hepatomegaly with tenderness to palpation over the liver. An abdominal ultrasound reveals a welldefined hypoechoic mass.

What is the most likely pathogen responsible for this patient’s symptoms?

A. Entamoeba histolytica
B. Candida albicans
C. Escherichia coli
D. Diphyllobothrium latum
E. Klebsiella pneumoniae

Correct Answer is A

Comment:

Entamoeba histolytica. Most infections due to the parasite Entamoeba histolytica are asymptomatic; however, this pathogen can cause invasive colitis presenting as dysentery. A common extraintestinal manifestation is liver abscess, which presents with fever and right upper quadrant abdominal pain. This patient recently emigrated from an endemic country and has suggestive symptoms of amebiasis complicated by a liver abscess. Diagnosis can be made with abdominal imaging and stool studies, and treatment is with both metronidazole and paromomycin (to eliminate luminal cysts). Amebic liver abscesses do not need to be drained and are usually treated successfully with medical therapy alone.

(B, E) Streptococcal species, S. aureus, Candida, and Klebsiella are all causes of liver abscess; however, the presentation of dysentery and recent immigration make amebiasis more likely. Escherichia coli, Campylobacter, and Salmonella can all cause invasive diarrhea but are not associated with liver abscesses. Of note, Salmonella can cause hepatosplenomegaly and also establish itself in a chronic carrier state in the gallbladder; however, this patient does not have other features of typhoid fever (“rose spot” rash, relative bradycardia, etc.). Diphyllobothrium latum is a tapeworm that produces GI symptoms and can present with megaloblastic anemia (due to parasitic absorption of dietary vitamin B12). Coccidioides is common in Arizona, but produces pulmonary symptoms; when it disseminates, it typically disseminates to the skin, meninges, or bone.