Question
Read the following clinical history and answer the following Mother of a small child was complaining about passing half an inch pale white motile worms in stool.
- (a) What is the probable diagnosis. 1 mark(s)
- (b) What sample will you collect from the patient. 1 mark(s)
- (c) What do you expect to see in light microscopy. 4 mark(s)
- (d) What would be the child’s symptoms. 2 mark(s)
- (e) What are the complications expected 2 mark(s)
Answer
a) Probable diagnosis: Enterobiasis (pinworm infection), caused by Enterobius vermicularis — passage of small (half-inch/~1 cm), pale-white, motile worms in the stool of a child is classical for the adult female pinworm.
b) Sample to collect: a perianal swab (Scotch/cellophane tape test/NIH swab), taken early in the morning before bathing or defecation — since the gravid female worm migrates out of the anus at night to lay her eggs on the perianal skin, eggs are rarely found in a routine stool sample, making the perianal swab the specimen of choice.
c) Expected light microscopy findings:
- On the perianal swab/tape — characteristic Enterobius vermicularis eggs: asymmetrically oval, flattened on one side (“D-shaped”), thin-shelled, colourless, typically containing a fully developed larva.
- If an adult worm is examined directly — a small, white, thread-like nematode with a characteristic pointed tail (female) and a prominent cephalic alae (wing-like cuticular expansions) at the anterior end.
d) Child’s symptoms: intense perianal (and sometimes perineal/vulval in girls) itching, particularly worse at night (when the female worm migrates to lay eggs) — often causing disturbed sleep, irritability, and, from scratching, secondary bacterial skin infection (excoriation); many infected children are otherwise asymptomatic or have only mild gastrointestinal discomfort.
e) Complications: perianal/perineal excoriation and secondary bacterial infection from scratching; vulvovaginitis in girls (from aberrant worm migration into the genital tract); rarely, appendicitis (from worm migration into the appendiceal lumen); disturbed sleep and behavioural disturbance from nocturnal itching; and reinfection/household transmission is common given the ease of egg spread via contaminated hands, bedding, and clothing (autoinfection via hand-to-mouth transfer of eggs from scratching is also common).