26 July 2007 – Case of the Week #90

 

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Case of the Week #90

 

Clinical History

 

A 33 year old woman presented with clinical appendicitis.  An appendectomy was performed.

 

Micro Images: image #1#2#3

 

What is your diagnosis?

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

Diagnosis:

 

Enterobius vermicularis (pinworm)

 

Discussion

 

The appendix shows no significant acute inflammation, ulceration, granulomas, dysplasia or malignancy.  However, there are adults of the species Enterobius vermicularis, with no associated inflammatory reaction.

 

Enterobius, previously known as Oxyuris vermicularis, is usually identified in the appendix of children ages 7-11 years as an incidental finding.  A cluster of worms may cause a mass.  There is at most a mild association with appendicitis (Pediatr Surg Int 2004;20:372, Southeast Asian J Trop Med Public Health 2007;38:20)

 

The diagnosis is usually not difficult, as long as one does not dismiss the worms as vegetable matter.  Enterobius is the most common helminthic infection in children, and affects all social strata in the US.  The worms reside in the cecum, and average 1.3 cm long.  They have prominent lateral spikes on cross section.  The eggs are 50 x 20 microns (images), and are often deposited at night on the perianal skin, causing pruritis ani, irritability and loss of sleep.  The eggs can be diagnosed with the cellulose tape technique on the perianal skin when the child wakes up.  Adult worms may migrate to the lower genital tract and cause a granulomatous reaction.

 

The differential may include other GI infestations.  Ascaris lumbricoides is a common intestinal roundworm, affecting 1 billion people worldwide.  It is large, ranging from 15-35 cm, and is usually identified grossly.  Unlike Enterobius, it has a smooth cuticle.  Its eggs are 60 x 45 microns, with a thick transparent hyaline shell covered by an albuminous coat.

 

Trichuris trichiura (whipworm) has a whiplike head, and attaches to intestinal mucosa via a long, slender anterior end.  The males have coiled tails.  The eggs are barrel shaped, 50 x 22 microns, with two polar plugs.

 

References: Centers for Disease Control

 

 

Nat Pernick, M.D., President
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