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Case #458 - December, 2017

A 69-year-old male, with recent travel to Peru, was undergoing a routine colonoscopy performed as a screen for colorectal cancer. The patient was asymptomatic and a stool ova and parasite examination (O & P) performed prior to the procedure was negative. However, the gastroenterologist recovered a worm from the ascending colon during the procedure and sent it to the pathology laboratory for identification. Figures AC show what was observed on hematoxylin and eosin (H & E) stained slides. Eggs seen inside the worm measured 50 x 25 micrometers on average. What is your diagnosis? Based on what morphologic features.

This case and images were kindly provided by Keck Medical Center or University of Southern California.

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Figure A

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Figure B

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Figure C

parasitic image answer

Figure A

parasitic image answer

Figure B

parasitic image answer

Figure C

This was a case of enterobiasis caused by Enterobius vermicularis (pinworm). Diagnostic morphologic features include:

  • The cephalic expansions  (black arrows, Figure A).
  • Esophagus (purple arrows, Figure A) and anterior end of esophageal bulb (red arrow, Figure A).
  • Eggs within the worm flattened on one side (blue arrows, Figures B and C) consistent with the species.
  • Average egg size provided is within the range for E. vermicularius.
  • Anatomical recovery site of the worm – the colon.

 

More on enterobiasis: https://www.cdc.gov/dpdx/enterobiasis/index.html

Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.

DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.

Page last reviewed: February 28, 2018