This week's case was generously donated by Dr. Richard Bradbury. A patient living in The Gambia presented with high fever, body aches, and altered consciousness. Images from the Giemsa-stained thick and thin blood films are shown below.
Due to a shortage of coartem, quinine was administered. Shortly afterwards, the patient's urine turned dark brown:
What is this condition, and what is it caused by?
This week's case features the intestinal biopsy of a middle aged man with abdominal pain and diarrhea. The astute pathologist noted these small objects (~20 microns in greatest dimension) associated with ulcerated colonic mucosa. Stain is hematoxylin and eosin (10x, 40x, and 100x objectives). What is your diagnosis?
Answer to the Parasite Case of the Week 778: Amebiasis due to Entamoeba histolytica.
As noted by Dr. Jacob Rattin, "It looks like there is ulceration in the adjacent mucosa and Entamoeba histolytica trophozoites with visibly ingested red blood cells." Several others also noted the ingested RBCs within the trophozoite cytoplasm.
When seen in stool specimens, the presence of RBCs within Entamoeba trophozoites allows us to presumptively call this E. histolytica rather than one of the identical-appearing amebae such as E. dispar. However, in this case, we have another important clue that allows us to presumptively identify the ameba, even if we don't see ingested RBCs: the presence of trophozoites associated with or invading into the ulcerated mucosa. E. dispar is not considered a pathogen, and other doppelgangers (e.g., E. moshkovskii, E. bangladeshi) have not been definitively shown to be pathogenic. Thus, the presence of invasive Entamoeba trophozoites points us towards E. histolytica. Note that the trophozoites look somewhat different in tissue than they do in stool as the central chromatin dot is often not present. However, the outer rim of chromatin is easily visible.
