A mother says her 2-year-old daughter has had 1 to 2 weeks of perineal and perianal itching. She notes that the itching occurs mostly at night, but she denies fevers, diarrhea, or emesis. The girl spends time in a “Mother’s Day Out” program 3 days per week but otherwise is always with her mother. On examination, the perianal area is red and irritated; the anal sphincter tone is normal, and you find no evidence of penetrating trauma. The perineal area is similarly red and excoriated. Other than a slight whitish vaginal discharge, the child’s diaper area is clean.
What is the most likely diagnosis?
How can you confirm the diagnosis?
What is the best management for this condition?
ANSWERS TO CASE 38: Pinworms
Summary: A 2-year-old healthy girl with several weeks of nocturnal perianal and perineal pruritus.
• Most likely diagnosis: Infection with Enterobius vermicularis (pinworms).
• Confirm the diagnosis: Cellophane tape test with microscopy to identify pin-worm eggs (Figure 38-1).
Figure 38-1. Pinworm (Enterobius vermicularis) ova on microscopy. (Reproduced, with permission, from Rudolph CD, Rudolph AM, Hostetter MK, Lister G, Siegel NJ, eds. Rudolph’s Pediatrics. 21st ed. New York, NY: McGraw-Hill; 2003:1106.)
• Best management: Mebendazole, pyrantel pamoate, or albendazole in a single dose, treating the entire family.
1. Describe the presentation of E vermicularis infection in the pediatric population.
2. Explain the methods of treatment and prevention of reinfection.
This patient has the typical history for pinworm infection. Although sexual abuse is possible, it is unlikely given the history and examination. Poor personal hygiene is another common problem in 2-year-olds who are toilet training and not cleaning themselves adequately. This results in perianal itching and irritation, yet the genital examination will be essentially normal. Occasionally, overzealous cleaning results in similar symptoms.
Enterobius vermicularis Infection
NEMATODE (ROUNDWORMS): Cylindrical organisms, with thousands of different species, only a few of which are parasitic (Table 38-1). Nematode infection is one of the most common types of infection in humans.
Table 38-1 • COMMON NEMATODE INFECTIONS IN HUMANS
A patient with perianal itching, especially at night, should be evaluated for E vermicularis infection. Unlike many other parasites, feces examination for ova is not useful because the eggs are small and few. Some parents may see a worm in the stool, but E vermicularis is difficult to identify positively with the naked eye. Instead, cellophane tape is applied to the perianal region in the early morning; from this tape E vermicularis eggs may be identified with microscopy. These eggs are infectious; proper infection control practices are indicated.
Enterobius vermicularis infection is the most common nematode infection in North America, and humans are the only natural host. Risk factors include exposure to other children in a day care environment or in the home. The adult worm is approximately 1 cm long and lives in the human GI tract, rarely migrating to the appendix, spleen, liver, bladder, and vagina. The pinworm life cycle begins when female worms migrate to the perianal region to deposit their eggs. Within 6 hours a larva is present in each ovum; the larvae are viable for up to 20 days. These eggs are subsequently transferred to clothes, fingers (from itching), and bed sheets. An infection results upon egg ingestion. The larvae “hatch” in the duodenum and grow to adult worms in 4 to 6 weeks.
Many infected patients are asymptomatic. The symptom described most frequently is nocturnal perianal itching, a result of worm and ova hypersensitivity. The gravid worms occasionally migrate to the perineal area, resulting in vaginal itching and discharge. Although bruxism historically has been related to pinworm infection, perianal itching is the only consistently reported symptom.
Some experts recommend treating the entire family (but at least washing all potentially infected bedding); others suggest global treatment only in recurrent cases. Treatment can be with mebendazole, albendazole, or pyrantel pamoate in a single dose. Often a second dose is given 2 weeks after the first dose to eliminate any new worms released from ova ingested proximate to the treatment time.
38.1 A mother states that her 4-year-old son has had 2 days of “buttocks pain.” She reports several blood-streaked stools and frequent scratching of the area. He is afebrile, but his perianal region is bright red with a clearly demarcated erythematous border. The area is diffusely tender, but no nodularity, fluctuance, or trauma is found. Appropriate diagnostic testing and therapy include which of the following?
A. Stool sample for ova and parasites; treatment with albendazole
B. Cellophane tape test for ova; treatment with albendazole
C. Rapid streptococcal test of the anal area; oral antibiotics
D. Blood culture; parenteral antibiotics
E. Administration of diaper rash ointment
38.2 A 6-year-old boy who recently moved from the southeastern United States complains of “something coming out” of his buttocks while straining during defecation; it seems to resolve when he relaxes. He also complains of abdominal pain and bloody stools for the last week. Examination reveals a normal external anus without evidence of trauma. When straining, he produces a pink mucosal mass from his anus; it returns when he relaxes. Initial diagnostic evaluation should include which of the following studies?
A. Cellophane tape test upon morning awakening
B. Stool for ova and parasites
C. Rectal culture
D. Abdominal ultrasonography
E. Herpes culture
38.3 A mother brings a stool sample for your review. In the stool are several 15- to 20-cm long, round, whitish worms. You initiate treatment with which of the following?
38.4 A 14-year-old adolescent male with HIV and AIDS presents for a physical examination prior to traveling to Southeast Asia. In counseling him on health risks in the area, you mention that he must always wear shoes to help prevent Strongyloides infection, which is particularly dangerous to him for which of the following reasons?
A. His antiretroviral medications make him more susceptible.
B. His immunodeficiency will make eradication impossible.
C. Antiparasitic agents are not available in Southeast Asia.
D. Teenagers typically have severe disease when infected.
E.Strongyloides can develop a “hyperinfection” in immunocompromised hosts.
38.1 C. Although diagnostic considerations should include pinworm infestation (as well as sexual abuse, contact diaper rash, and candidal diaper rash), the presentation is more consistent with perianal cellulitis. Pinworm infection usually does not cause blood-streaked stool, and any erythema associated with it is not well demarcated. Perianal cellulitis is commonly caused by Streptococcus and usually responds to oral or topical (mupirocin [Bactroban]) antibiotics.
38.2 B. Pinworms are not known to cause rectal prolapse, but whipworms (Trichuris trichiura) are. The whipworm nematode lives in warm and humid areas and is commonly found in the rural southeastern United States. Routine microscopy for ova is sufficient for the diagnosis (whipworms produce many more ova than do pinworms). Treatment is albendazole or mebendazole. Cystic fibrosis should be a consideration in a child with rectal prolapse, although the history should also include frequent pneumonias, failure to thrive, or foul-smelling stools.
38.3 B. Worms of this size and description typically are Ascaris; treatment is mebendazole or albendazole. Amoxicillin is an antibacterial agent. Praziquantel, niclosamide, and paromomycin are effective against cestodes (tapeworms) and are not recommended for nematodes.
38.4 E. The life cycle of Strongyloides does not require a period outside the host. Therefore, the organism can “autoinfect” the host (larvae in the intestines move through the intestinal wall, into the circulation, through the lungs, and back into the intestines). This autoinfection can lead to disseminated strongyloidiasis in immunocompromised hosts with massive invasion of organs and subsequent tissue destruction; sepsis with gram-negative intestinal organisms can result.
Patients with nocturnal perianal itching are evaluated for Enterobius vermicularis infection.
Typical stool ova and parasites studies may not identify Enterobius vermicularis ova (the count is low). A cellophane tape test is more useful to confirm the diagnosis.
Cherian T. The nematodes. In: McMillan JA, Feigin RD, DeAngelis CD, Jones MD, eds. Oski’s Pediatrics: Principles and Practice. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006:1361-1369.
Dent AE, Kazura JW. Enterobiasis (enterobius vermicularis). In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics, 19th ed. Philadelphia, PA: Elsevier; 2011:1222.
Merritt DF. Vulvovaginitis. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics, 19th ed. Philadelphia, PA: Elsevier; 2011:1865-1869.
Oberhelman RA. Enterobiasis (pinworm). In: Rudolph CD, Rudolph AM, Lister GE, First LR, Gershon AA, eds. Rudolph’s Pediatrics. 22nd ed. New York, NY: McGraw-Hill; 2011:1190-1191.