Sunday, January 15, 2023

Answer to Case 707

 Answer to the Parasite Case of the Week 707: Sarcocystis species. Molecular testing is required for identification of the causative species. 

This case shows a single intramuscular sarcocyst containing multiple bradyzoites. The clinical history and epidemiology also supports a diagnosis of sarcocystosis.

Many of you rightly suggested that the differential diagnosis includes Toxoplasma gondii, a related apicomplexan parasite which can form similar-appearing cysts in tissues throughout the body. Toxoplasmosis involving skeletal muscle is seen primarily in profoundly immunocompromised individuals with widely disseminated disease. When T. gondii is in the clinical diagnosis, then species-specific immunohistochemistry and/or PCR can be used to confirm the diagnosis.  

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