Monday, May 14, 2018

Case of the Week 494

A patient with recent travel to southern Africa presented with fever and myalgias. The following are representative views from Giemsa-stained thick and thin peripheral blood films.

Any thoughts on the percentage of parasitemia?
What should the laboratory do when seeing this?

Sunday, May 13, 2018

Answer to Case 494

Answer: Malaria due to Plasmodium falciparum; >20% parasitemia
There were lots of great suggestions for what the lab should do after making this identification. The step of primary importance is to urgently contact the clinical team to relay the result and ensure they understand the importance of the diagnosis. In my laboratory we treat all malaria diagnoses as critical results. In this case, the causative agent (P. falciparum) and the high parasitemia (>2%) make this call even more urgent, since the patient is at very high risk of death from his infection and requires immediate treatment.

In addition to antimalarial treatment (e.g. IV quinidine or artesunate), red blood cell exchange may also be performed for patients with >10 % parasitemia. While the United States Centers for Disease Control and Prevention (CDC) no longer recommends red cell exchange for severe malaria, many other groups such as the American Society for Apheresis (ASA) feel that it is still warranted in life-threatening infections such as this one. You can read the arguments for red blood cell exchange for malaria with >10% parasitemia here:

CDC paper arguing AGAINST red cell exchange for severe malaria:

Counter argument from the ASA:

Thanks to everyone who wrote in on this case, and kudos to those who took the time to calculate the % parasitemia!

Monday, May 7, 2018

Case of the Week 493

It's time for our monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp.

The mother of a 5 year-old Belgian patient brought in a small worm-like structure (measuring 12 mm in length) along with a fecal sample. Microscopic examination of the worm-like structure using low power magnification revealed the following:
Anterior end:
A direct wet mount was made from the stool sample. The structures that are found in the wet mount are shown in following image and videoclips.
Check out these cool videos (you may need to press play twice)

Sunday, May 6, 2018

Answer to Case 493

Answer: Enterobius vermicularis adult female and eggs (containing viable larvae). I hope you all got to see the beautiful video of 'baby's first steps' (or wriggles?) that Idzi provided showing a larva hatching from an egg.

The diagnostic features include prominent cervical alae, bulbous esophagus, pointed 'pin-like' tail, and "D" shaped eggs, with flattening on one side.

As Florida Fan mentioned, Blaine did a fabulous job replicating these eggs in his Halloween costume last year.

AND, he left some presents behind!

Tuesday, May 1, 2018

Case of the Week 492

The following objects were seen on a thin blood smear that was made to evaluate a patient for malaria. No further history is available. Images courtesy of Emily Fernholz.


Monday, April 30, 2018

Answer to Case 492

Answer: Histoplasma capsulatum
This small oval-shaped fungus has a very similar appearance to the amastigotes of Leishmania species (and Trypanosoma cruzi), as well as the tachyzoites of Toxoplasma gondii. It is therefore always in my differential of small intracellular objects when I am looking at blood smears, bone marrow aspirates and tissue sections. All of these objects measure 2 to 5 micrometers in greatest dimension and can be found within phagocytic cells. However, there are several key differentiating features that allow for a correct identification to be made:

1. Leishmania spp. amastigotes - have a single nucleus and rod-shaped kinetoplast. They are found within macrophages/monocytes.
2. T. cruzi amastigotes - are indistinguishable from Leishmania amastigotes but have a different tissue tropism (e.g. cardiac and smooth muscle cells) and associated clinical presentation.
3. Toxoplasma gondii tachyzoites - are arc-shaped (but can appear oval in tissue) and have a single nucleus with no kinetoplast. They can infect any nucleated cell.
4. Histoplasma capsulatum yeasts - are found within macrophages/monocytes and divide by narrow-based budding. As Sugar Magnolia mentioned, their cell wall does not take up many stains well (e.g. Giemsa, H&E), and therefore they appear to have a surrounding capsule (sometimes termed a pseudocapsule). This is where the species name, capsulatum, comes from. A silver fungal stain (e.g. Gomori methenamine silver) will stain all of the yeast including its cell wall. In contrast, amastigotes and tachyzoites do NOT stain with GMS.

It's important to note that other yeasts such as Penicillium marneffei and Cryptococcus neoformans will also stain with silver fungal stains and may have a similar appearance to H. capsulatum in peripheral blood films. They can be differentiated through a careful examination of several morphologic features; Cryptococcus neoformans has a true capsule, unlike H. capsulatum, and exhibits more size variability, whereas Penicillium marneffei divides by formation of transverse septations rather than budding.

Whew! That was a long explanation. Kudos to my excellent parasitology technologists who correctly detected and identified the H. capsulatum on the malaria smears. I later found out that the patient was severely immunocompromised with AIDS - a common scenario for histoplasmosis detected on peripheral blood films.

Monday, April 23, 2018

Case of the Week 491

This week's case is courtesy of Dr. Delgado and the Yale Pathology department. The patient is young adult male with extensive travel throughout Europe, Central America and Africa, who presented fever, drenching night sweats, extreme fatigue, cervical lymphadenopathy and splenomegaly. CBC showed pancytopenia. The following are from the H&E-stained bone marrow biopsy and Giemsa-stained aspirate.


Sunday, April 22, 2018

Answer to Case 491

Answer: Visceral leishmaniasis due to Leishmania species (Leishmania donovani complex or L. tropica). As noted by Brady Page, Anon, Florida Fan, William Sears, and Daniel Skipper, the diagnosis can be easily secured by identifying the amastigotes within mononuclear phagocytes. Each amastigote has a small eccentric nucleus and rod-shaped kinetoplast, giving the so-called "dot-dash" pattern (thank you @JClinMicro)
 And thank you to our poet, Blaine, who gave us the following:
Sheesh! This guy has Leish! 
Maybe from sandflies at the beach? 
PCR should be within reach, 
in case there is a call for Pentostam to release!

Monday, April 16, 2018

Case of the Week 490

This week's case is generously donated by Florida Fan. The following object was submitted to the laboratory for identification. It had been retrieved during colonoscopy from the cecum of a 40-year-old man.


Sunday, April 15, 2018

Answer to Case 490

Answer: Female Trichuris sp.
The most likely etiology is T. trichiura. However, as several readers mentioned, human infection with T. vulpis has rarely been reported and the adult worm has a similar appearance. The two worms are differentiated primarily by their eggs, with T. vulpis eggs being nearly twice as large as T. trichiura eggs. The only eggs we see in this case are immature and intrauterine; therefore it is not possible to use the eggs to help us differentiate the two worms.

Here are some of the key diagnostic features of this case:
Note that the head is at the slender end (all the better for embedding into the large bowel mucosa), while the larger end (containing the uterus and eggs) hangs free in the bowel lumen. We can tell that this is a female worm because of the eggs in the uterus (below) and because the tail is not coiled like a male's tail would be.