Pathology Cheat Sheet
Three Paths, Three Tissues
Malaria, cysticercosis and leprosy for NEET-PG: falciparum sequestration, Schuffner dots, neurocysticercosis, and tuberculoid versus lepromatous leprosy.
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Three Paths, Three Tissues
Malaria, cysticercosis and leprosy for NEET-PG: falciparum sequestration, Schuffner dots, neurocysticercosis, and tuberculoid versus lepromatous leprosy.
The pathogenesis and pathology of three endemic parasitic and mycobacterial diseases: malaria, cysticercosis, and leprosy.
High-yield lines
- Plasmodium falciparum causes the most severe malaria, with multiple ring forms in non-enlarged red cells and banana-shaped gametocytes.
- Falciparum malaria causes cerebral malaria through microvascular sequestration of parasitised red cells in cerebral vessels.
- Plasmodium vivax and ovale show Schuffner dots and enlarged infected red cells and form hypnozoites causing relapse.
- Malaria is diagnosed on Giemsa-stained thick and thin blood films, with ring forms showing blue cytoplasm and a red chromatin dot.
- Cysticercosis is caused by the larval Cysticercus cellulosae of the pork tapeworm Taenia solium acquired by ingesting eggs by the feco-oral route.
- Eating undercooked pork causes intestinal taeniasis with the adult worm, not tissue cysticercosis.
- Neurocysticercosis is the most common cause of acquired epilepsy in the developing world.
- A viable cysticercus suppresses host immunity, so symptoms arise when the cyst degenerates, producing a ring-enhancing lesion.
- Leprosy is caused by Mycobacterium leprae, which prefers cooler temperatures and infects Schwann cells and dermal macrophages.
- Tuberculoid leprosy has strong Th1 immunity, few bacilli, well-formed nerve-centred granulomas, and a positive lepromin test.
- Lepromatous leprosy has minimal immunity, abundant bacilli, foamy Virchow lepra cells, and a negative lepromin test.
- Lepra bacilli in tissue are demonstrated with the modified Ziehl-Neelsen Fite-Faraco stain.
Mapped competency codes
- PA10.1
- PA10.2
- PA10.3
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This summary maps to PA10-infections-and-infestations.
Frequently Asked Questions
How is cysticercosis acquired?
By ingesting eggs of Taenia solium through the feco-oral route, whereas eating undercooked pork causes intestinal taeniasis with the adult tapeworm.
What blood film features indicate falciparum malaria?
Multiple ring forms per red cell in normal-sized red cells, absence of Schuffner dots, and banana-shaped (crescentic) gametocytes.
How do the tuberculoid and lepromatous poles of leprosy differ?
Tuberculoid leprosy has strong cell-mediated immunity with few bacilli and nerve granulomas, while lepromatous leprosy has weak immunity, many bacilli, and foamy Virchow lepra cells.
Which stain demonstrates Mycobacterium leprae in tissue?
The modified Ziehl-Neelsen stain (Fite-Faraco), because the standard acid-fast stain is too harsh and may decolorise lepra bacilli.
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