Vol

DEPARTMENT OF PATHOLOGY The Johns Hopkins Medical Institutions

Vol. 18, No. 2
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Monday, January 11, 1999

Provided by Leslie Edwards Reger, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.

The Johns Hopkins Hospital. Information provided by Dr. Ann Smith, Department of Pathology.

Case Report: A 12-year-old previously healthy white female came to the hospital complaining of abdominal pain and diarrhea. She denied any fever or vomiting. The pain and diarrhea began approximately two weeks after visiting Mexico. While in Mexico she ate raw vegetables and seafood but she did not eat any raw meat. Physical examination revealed right lower quadrant tenderness and laboratory analysis revealed a leukocytosis. The patient was referred to the surgery team for evaluation and subsequently underwent an appendectomy. The appendix was sent to surgical pathology.

Histologic Diagnosis: H & E sections of the appendix revealed increased eosinophils, focal eosinophil microabscesses, and cross sections of Enterobius vermicularis (pinworm). There were no findings to suggest inflammatory bowel disease.

Discussion: The infestation of man with Enterobius vermicularis has been reported for thousands of years; in 1634, Fabrius reported the presence of a pinworm in the appendix. However, although pinworms are not an uncommon finding in the stools of children, abdominal findings secondary to pinworms are considered to be relatively rare.

The mature pinworm lives and reproduces in the terminal ileum and proximal large intestine. After fertilization, the male worm dies and the female migrates to the anus where she lays her eggs on the perianal skin. The female migration usually occurs at night and the worm ova cause an intolerable itching accounting for the typical signs and symptoms of erythema and pruritis ani seen in children. The pinworms can subsequently enter the vagina and migrate up the genital tract where they can invade the ovaries and even the omentum.

Several authors have looked at the relationship of pinworm infestation to appendicitis. Studies out of England have reported from between 1.5% to 4.2% prevalence of pinworm appendicitis in specimens removed for presumptive acute appendicitis.

The histologic findings revealed, however, that the pinworms are most commonly seen in association with chronic inflammatory changes and not with acute inflammation. Other histologic characteristics include prominent eosinophils and granulomatous inflammation which must be distinguished from chronic changes seen in inflammatory bowel disease.

Of interest, one study reported that male pinworms were more commonly seen in appendiceal specimens than female pinworms (116 cases versus 20). Whether or not the fact that the male pinworm is significantly smaller in size (2-5mm) compared to the female worm (8-13mm) accounts for this finding is unknown.

Although pinworms are usually asymptomatic inhabitants of the intestine, when they do cause symptoms there can be a spectrum of nonspecific gastrointestinal complaints. Because the cause of abdominal pain in children is often difficult to diagnose pinworm appendicitis and even salpingitis should be considered.

References:

1. Budd JS, Armstrong C. Role of Enterobius vermicularis in the aetiology of appendicitis. Br J Surg 1987 Aug; 74 (8): 748-9.

2. Nutting SA, Murphy F, Inglis FG. Abdominal pain due to Enterobius vermicularis. Can J Surg 1980 May; 23 (3): 286-7.

3. Williams DJ, Dixon MF. Sex, Enterobius vermicularis and the appendix. Br J Surg 1988 Dec; 75 (12): 1225-6.