Monday, September 14, 2009
Case of the Week 84
The following images are from a peripheral blood smear from a 93 year old male from Connecticut. No travel history is received.
Answer to Case 84
Answer: Babesia spp.
Congratulations to all of my viewers who got this correct.
Babesiosis is a tick-borne disease, found in North America, Europe, and Asia. It is a mimic of infection with Plasmodium falciparum (which was the 2nd most common answer that viewers gave), since the infected RBCs are not enlarged, the rings are small (1/3 the size of the RBC or smaller), and multiple infections per cell are common. Fortunately, several features allow for differentiation of Babesia spp. from P. falciparum.
First, note that the size of the organisms within RBCs is variable, and that some forms are extremely small (<1/5 the diameter of the RBC). This is typical for babesiosis, and not for P. falciparum.
Second, Babesia spp. tend to produce atypical forms, with multiple chromatin dots, 'double' rings, and chromatin 'tails' such as seen here:
Babesia rings may also be seen outside of the RBC, in the extracellular space.
If you're really lucky, you will see the classic tetrad formation or "Maltese cross" formed when this organism undergoes binary fission. Although this is the image that is commonly shown in textbooks, it is much rarer in real life.
Finally, the travel/exposure history of the patient is very helpful. It wasn't initially available in this case, but we were later told that the patient had no travel history outside of the U.S. He lived in Connecticut which is endemic for Babesia microti.
This was a challenging case, so thanks to all who were brave enough to write in!
Congratulations to all of my viewers who got this correct.
Babesiosis is a tick-borne disease, found in North America, Europe, and Asia. It is a mimic of infection with Plasmodium falciparum (which was the 2nd most common answer that viewers gave), since the infected RBCs are not enlarged, the rings are small (1/3 the size of the RBC or smaller), and multiple infections per cell are common. Fortunately, several features allow for differentiation of Babesia spp. from P. falciparum.
First, note that the size of the organisms within RBCs is variable, and that some forms are extremely small (<1/5 the diameter of the RBC). This is typical for babesiosis, and not for P. falciparum.
Second, Babesia spp. tend to produce atypical forms, with multiple chromatin dots, 'double' rings, and chromatin 'tails' such as seen here:
Babesia rings may also be seen outside of the RBC, in the extracellular space.
If you're really lucky, you will see the classic tetrad formation or "Maltese cross" formed when this organism undergoes binary fission. Although this is the image that is commonly shown in textbooks, it is much rarer in real life.
Finally, the travel/exposure history of the patient is very helpful. It wasn't initially available in this case, but we were later told that the patient had no travel history outside of the U.S. He lived in Connecticut which is endemic for Babesia microti.
This was a challenging case, so thanks to all who were brave enough to write in!
Tuesday, September 1, 2009
Case of the Week 83
The following "skin tag" was removed from the groin of a middle-aged male.
Identification? (CLICK ON IMAGES TO ENLARGE)
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Identification? (CLICK ON IMAGES TO ENLARGE)
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Answer to Case 83
Answer: Hard Tick
This was definitely a challenging one - including for me when I first saw this case. I think that most of us are not used to seeing ticks cut in histologic section (usually this isn't necessary for identification!), but there are some characteristic features that allow for easy identification of this case.
First, notice that the organism is mostly external to the skin, and is inserted only at one end. This is the classic presentation for a tick, and would argue against a botfly larva which is mostly inserted into the skin.
In addition, there are useful identifying histologic features as outlined in the image below, including a thick sclerotized cuticle, well-developed skeletal muscle near the mouth parts, and the mouthparts themselves, if present. (CLICK ON IMAGE TO ENLARGE)
This was definitely a challenging one - including for me when I first saw this case. I think that most of us are not used to seeing ticks cut in histologic section (usually this isn't necessary for identification!), but there are some characteristic features that allow for easy identification of this case.
First, notice that the organism is mostly external to the skin, and is inserted only at one end. This is the classic presentation for a tick, and would argue against a botfly larva which is mostly inserted into the skin.
In addition, there are useful identifying histologic features as outlined in the image below, including a thick sclerotized cuticle, well-developed skeletal muscle near the mouth parts, and the mouthparts themselves, if present. (CLICK ON IMAGE TO ENLARGE)
Sunday, August 23, 2009
Case of the Week 82
The following thin Giemsa-stained blood smear is from a missionary who just returned from Tanzania. (CLICK ON IMAGES TO ENLARGE)
Identification?
What are the identifying features of this case?
Identification?
What are the identifying features of this case?
Saturday, August 22, 2009
Answer to Case 82
Answer: Plasmodium falciparum
The key identifying features are:
1. The infected RBCs are not enlarged (compared to the enlarged RBCs infected by P. ovale and P. vivax.
2. Parasite rings are small and delicate, occupying approximately 1/3 of RBC diameter.
3. Applique or Accole forms are present. These are rings that appear to be 'stuck' onto the edge of the RBC.
4. Presence of Maurer's clefts or dots. These are cytoplasmic structures derived from the malaria parasite. They have a similar appearance to the 'stippling' seen in infection with P. ovale and P. vivax, but the dots are fewer and larger. In order to see Maurer's clefts, it is essential to have your malaria buffer at the proper pH, that is, at 7.2.
Maurer's clefts and stippling are not seen in infection with P. malariae.
The key identifying features are:
1. The infected RBCs are not enlarged (compared to the enlarged RBCs infected by P. ovale and P. vivax.
2. Parasite rings are small and delicate, occupying approximately 1/3 of RBC diameter.
3. Applique or Accole forms are present. These are rings that appear to be 'stuck' onto the edge of the RBC.
4. Presence of Maurer's clefts or dots. These are cytoplasmic structures derived from the malaria parasite. They have a similar appearance to the 'stippling' seen in infection with P. ovale and P. vivax, but the dots are fewer and larger. In order to see Maurer's clefts, it is essential to have your malaria buffer at the proper pH, that is, at 7.2.
Maurer's clefts and stippling are not seen in infection with P. malariae.
Monday, August 10, 2009
Case of the Week 81
The following worms were identified in this papanicolaou-stained sputum from a 70 year old man being treated with chemotherapy for disseminated lung cancer. They measure approximately 500 micrometers in length. What is the most probable diagnosis? (CLICK ON IMAGES TO ENLARGE)
Sunday, August 9, 2009
Answer to Case 81
Answer: Probable Strongyloides stercoralis filariform (L3) larvae.
Congratulations to everyone who wrote in with the correct answer! You all recognized that these are nematode (round worm) larvae. The clinical history and presence of larvae in the sputum are most suggestive of S. stercoralis, although it is difficult to make out specific features from these photographs to make a definitive diagnosis. The fact that they are relatively elongated suggests that they are the 3rd stage larvae (L3 or filariform) which is the typical stage that is seen in the lung during autoinfection.
Congratulations to everyone who wrote in with the correct answer! You all recognized that these are nematode (round worm) larvae. The clinical history and presence of larvae in the sputum are most suggestive of S. stercoralis, although it is difficult to make out specific features from these photographs to make a definitive diagnosis. The fact that they are relatively elongated suggests that they are the 3rd stage larvae (L3 or filariform) which is the typical stage that is seen in the lung during autoinfection.
Monday, August 3, 2009
Case of Week 80
The following insect is a vector of 2 important South American viruses. Identification?
Bonus: list the viruses
Bonus: list the viruses
Answer to Case 80
Answer: Aedes aegypti mosquito
This is one of the most easily recognizable mosquitoes, due to its dark body and distinctive white markings. It closely resembles another human disease vector, A. albopictus (a.k.a. Asian Tiger mosquito), except that the latter has a single straight white stripe on its dorsal thorax instead of lateral curved stripes.
A. aegypti is the vector of Yellow Fever, Dengue, and Chikungunya virus. The former two viruses may be found in South America, and are the answer to the second question of this case.
This is one of the most easily recognizable mosquitoes, due to its dark body and distinctive white markings. It closely resembles another human disease vector, A. albopictus (a.k.a. Asian Tiger mosquito), except that the latter has a single straight white stripe on its dorsal thorax instead of lateral curved stripes.
A. aegypti is the vector of Yellow Fever, Dengue, and Chikungunya virus. The former two viruses may be found in South America, and are the answer to the second question of this case.
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