NBME Form 16 Practice Test

Think about schistosomiasis presenting with liver and spleen involvement in someone from Africa. The combination of abdominal pain, hepatosplenomegaly, ascites, and eggs seen in stool points to infection with a Schistosoma species that causes intestinal disease (such as Schistosoma mansoni). The drug of choice for schistosomiasis is praziquantel. It works by increasing the parasite’s cell membrane permeability to calcium, which leads to spastic paralysis and death of the adult worms in the mesenteric and portal venous systems. Once the adults are killed, egg production drops, reducing ongoing inflammation and portal hypertension and improving clinical symptoms. Other drugs listed target different parasites (nematodes or anaerobic protozoa) and are not as effective against Schistosoma, so praziquantel is the best choice here.