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A 28-year-old man presented to his primary care physician for hematochezia. He had previously lived for a few years in Uganda and frequently swam in the Nile River. After returning to the US, he experienced recurrent diarrhea. In April 2018, he had an appendectomy for acute appendicitis. In February 2019, 22 months after his return from Uganda, he developed intermittent hematochezia. He had no vomiting, fever, or weight loss during this time. On evaluation, vital signs were normal and abdominal examination showed a soft, nontender abdomen. Rectal examination was normal. A complete blood cell count and comprehensive metabolic panel were notable for a normal hemoglobin level and an absolute eosinophil count of 304 cells/μL. Results of testing including stool microscopy, HIV fourth-generation assay, hepatitis B serologies, and a rectal swab for gonorrhea and chlamydia were negative. A colonoscopy demonstrated granular mucosa in the rectum. Internal hemorrhoids were present, but there were no masses, vascular malformations, or other abnormalities. A biopsy of rectal tissue was obtained; histopathologic features are shown in the Figure.
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A. Prescribe praziquantel without further diagnostic testing
The key to the correct diagnosis in this patient is the histopathologic finding of granulomas containing schistosome eggs (Figure, black arrows) with lateral spines (Figure, blue arrow), consistent with Schistosoma mansoni, for which praziquantel is indicated (choice A). Although stool microscopy (choice B) is an appropriate first step, returning travelers often have low parasite burdens, so additional stool samples are low yield. The presence of schistosome eggs argues against tuberculosis as the cause of the granulomatous inflammation, so tuberculosis testing (choice C) and treatment (choice D) are not warranted.
Schistosomiasis is a parasitic infection caused by flukes. Schistosoma mansoni, found in Africa and the Arabian Peninsula, resides in mesenteric venules, leading to intestinal, hepatic, and/or pulmonary disease as a result of an immune response to migrating eggs that deposit in these organs.1 Infection is acquired through freshwater contact, from which larvae infect humans via skin penetration.2 Exposure to upper Nile River water is a risk factor for S mansoni acquisition. In one study, 17% of persons exposed to Ugandan Nile River water developed acute schistosomiasis.3
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Corresponding Author: Shana Gleeson, MD, Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, PO Box 208022, New Haven, CT 06519 (Shana.email@example.com).
Published Online: March 5, 2021. doi:10.1001/jama.2021.0368
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the patient for providing permission to share his information.
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