A 56-year-old Mexican man with prior renal transplantation and no recent travel presented with watery diarrhea, periumbilical pain, and nausea. One week prior he ate at a local food truck. He was afebrile, and initial stool studies showed no enteric pathogens and no ova or parasites. Decreasing his dose of mycophenolate for immunosuppression had no effect.
The diarrhea continued for several weeks, and colonoscopy appeared endoscopically normal. Multiple biopsies showed diffuse submucosal parasitic infection with Hymenolepis nana (Figures A, arrow and arrowhead and B).
Transplant infectious disease consultants treated him with a 25 mg/kg dose of praziquantel. Several months later, the diarrhea returned. Colonoscopy showed small worms undulating in the colonic submucosa (Figures C, arrow and D, arrows; Supplementary Video 1). He was re-treated with praziquantel. Public Health officers also visited his home and treated his partner.
Hymenolepis nana (H nana), or dwarf tapeworm, is the most common cestode to infect humans globally but is rare in adults. Irregular shedding decreases the sensitivity of stool studies, but additional stool sedimentation techniques can increase detection rates. This parasite can be passed between family members, leading to reinfection. This case should alert physicians to consider H nana in organ transplant recipients with chronic diarrhea and to biopsy the colon even when endoscopic appearance is normal.
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Published online: March 05, 2020
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Conflicts of interest The authors disclose no conflicts.
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© 2021 by the AGA Institute
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