Monday, March 30, 2009

Case of the Week 63

This is a related case to our previous one. The following were seen in snips of skin (collected without drawing blood) from a patient with severe dermatitis. Following collection, the skin samples were incubated in normal saline for 2 hours and examined under 1000x magnification. The patient is from South America.


Sunday, March 29, 2009

Answer to Case 63

Answer: Onchocerca volvulus microfilariae. These microfilariae are released from the adults which are confined in subcutaneous nodules (onchocercomas). The microfilariae then migrate throughout the dermis, causing intense itching and chronic skin changes. More debilitating is the eye involvement which leads to blindness; hence onchocerciasis is also known as "River Blindness." To confirm the diagnosis, these microfilariae could be fixed in alcohol and stained with Giemsa.

Also in the differential diagnosis is Mansonella streptocerca. This filarial worm also releases its microfilariae into the skin, but it does not cause severe disease and is restricted to Africa. If the skin snip was very bloody, then other microfilariae which are found in the peripheral blood must also be considered. This is why it is best to obtain "bloodless" skin snips. Giemsa staining of the worms will also allow for identification based on characteristic features of the microfilariae.

As Alasdair mentioned, this is typically thought of as an African disease. However, onchocerciasis is also found in Central and South America. Interestingly, the adult worms in South America tend to form onchocercomas in the head and neck region, whereas onchocercomas in Africa are classically located around the pelvis, abdomen, and knees. This is likely due to the biting preferences of the vector, the black fly (Simulium spp.).

Monday, March 23, 2009

Case of the Week 62

The following was seen on a slide prepared with unstained blood from a Sudanese immigrant. What is your preliminary diagnosis?

Initial view from 100x magnification

Higher magnification (1000x)

Sunday, March 22, 2009

Answer to Case 62

Great comments for this case!
Answer: microfilariae, not otherwise specified.

Although Loa loa, Wuchereria bancrofti, Mansonella spp. and Brugia spp. are all possibilities, we cannot determine the species identification without performing addition testing; specifically by making permanently stained smears of the fixed (dead) organism, and examining features such as the tail nuclei, length of the worm, and presence/absence of a sheath. Essentially, we need it to stop moving AND apply a special stain such as Giemsa or hematoxylin so that we can more adequately study its defining characteristics.

One commenter mentioned Strongyloides; this is also a possibility if the patient has disseminated strongyloidiasis, but is a less likely than the filariasis. Again, a permanently stained preparation would be necessary to make this diagnosis.

Finally, two commenters noted the presence of rouleaux formation (stacking of RBCs so that they resemble a stack of coins). I believe that this is an artifact, perhaps due to the type of anticoagulant used in this case.

Monday, March 16, 2009

Case of the Week 61

This week's case is a simple identification. Enjoy!

Sunday, March 15, 2009

Answer to Case 61

Alasdair said it well with "Ah Schistosoma japonicum.... the smooth skinned schisto couple!!"

This is indeed a male and female schistosome couple 'in copula'; note that the female is resting in the gynecophoric groove of the male. Schistosomes are the only human parasitic trematodes to have both separate sexes; the others (e.g. Fasciola, Clonorchis) are hermaphrodites. The below image demonstrates the female (arrow head) and male. Note the oral and ventral suckers (arrows) which are easily visible on the male. CLICK ON IMAGE TO ENLARGE

As Alasdair mentioned, S. japonicum is smooth skinned, compared to S. mansoni, which has a ridged cuticle.

Tuesday, March 10, 2009

Case of the Week 60

The following worm segment was submitted for examination. The objects within the worm measure approximately 60 microns in length. Identification? (CLICK ON IMAGES TO ENLARGE)

Monday, March 9, 2009

Answer to Case 60

Congratulations to Heather and Anonymous for getting the correct answer to this case! This is, indeed, Diphyllobothrium latum, the broad fish tape worm. It get's its nickname based on the fact that its proglottids are broader than they are long. Note the presence of the classic "rosette-shaped" uterus. Anonymous is also correct in that it's the longest tapeworm found in humans. Adults can reach up to 10 m (>30 ft) in length, with more than 3,000 proglottids!

As Heather mentioned, "The eggs are kinda shrunken/dehydrated-looking". This isn't uncommon when viewing the eggs inside the uterus, since they are immature. The staining and fixation procedure also likely affected the morphology. However, you can still make out the operculum in some of the photographs (marked by arrows), and the size is consistent with this organism.

Monday, March 2, 2009

Case of the Week 59

A small white object (approx 1 cm length) resembling a grain of rice was identified in the diaper of a 1 year old child. Manipulation of the object revealed the following microscopic objects (round objects individually measure 25 to 40 microns in diameter). CLICK ON IMAGES TO ENLARGE


Sunday, March 1, 2009

Answer to Case 59

Answer: Eggs of Dipylidium caninum, the double-pored dog tapeworm. This is the classic appearance of D. caninum eggs: multiple thin-shelled eggs with hooklets; the eggs being contained within packets or present singly. The packets typically contain 8-15 eggs; less eggs are present in the packets shown here and may reflect their premature extraction from the proglottid.

One hint regarding eggs that contain hooklets: these are likely to be cestode eggs. Eggs of nematodes and trematodes that infect humans do not not contain hooklets. The reverse is not true: not all cestodes capable of infecting humans have eggs with hooklets (e.g. eggs of the broad fish tapeworm, Diphyllobothrium latum).

D. caninum is typically found in children, and is acquired by ingestion of an infected flea such as the dog or cat flea (Ctenocephalides canis and Ctenocephalides felis, respectively).

A final note: one commenter suggested that these could represent eggs of a zoonotic cestode such as Inermicapsifer species which also has multiple eggs contained in a packet (referred to as an 'egg capsule'). Unlike D. caninum, the eggs of this organism cannot be seen easily while in the capsule. If the capsule is ruptured, 5 to 10 characteristic elongated eggs can be identified, which are recognizably different from the round eggs of D. caninum.