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  • • Severe perianal itching, often at night

    • When chronic, skin becomes white, leathery, and thickened

    • Usually idiopathic

    • Most patients have tried many over-the-counter preparations without relief

    • Agents may exacerbate the problem by keeping the perineum moist, causing further irritation, or by creating a contact dermatitis

    • Poor cleansing of the perineum may lead to irritation

    • Frequent washing with soaps and detergents dries the skin, also leading to pruritus

    • Pinworms (Enterobius vermicularis) are the most common cause of perianal itching in children

    • Pruritus may result from tight clothing, obesity, and living in a hot climate

    • When a specific cause cannot be found, it is considered idiopathic

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Epidemiology

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  • • Pinworms (E vermicularis) are the most common cause of perianal itching in children under 12 years of age

    • Enterobius (pinworm) is an intestinal roundworm (nematode) transmitted by ingestion of eggs

    • Adult male and female worms live in the colon

    • -At night the female migrates from the anus and releases thousands of fertilized eggs on the perianal skin

      -Eggs develop into larvae and become infectious

    • Reinfection occurs if eggs are carried into the mouth after scratching the perianal skin

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Symptoms and Signs

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  • • Severe perianal itching, often worse at night

    • Skin is thickened, white, and leathery in the chronic state

    • Skin is normal to weeping in the acute stage

    • In children with pinworms, perianal itching is most severe at night when the pinworm deposits its eggs on the perianal skin

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Laboratory Findings

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  • • Scotch tape test: Diagnosis of pinworms is made by applying cellophane tape to the perianal skin, which collects the eggs

    • Scrapings of the perianal skin viewed microscopically may reveal fungi or parasites

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  • • Associated with other perianal lesions that distort normal anal anatomy such as hemorrhoids, fistulas, fissures, tumors of the anorectum, previous surgery, and radiation therapy

    • Primary dermatologic diseases:

    • -Lichen planus

      -Atopic eczema

      -Psoriasis

      -Seborrheic dermatitis

    • Infectious etiology:

    • -Fungal (dermatophytosis, candidiasis)

      -Parasitic (E vermicularis, scabies, or pediculosis)

      -Bacterial superinfection

    • Contact dermatitis from local anesthetic creams or soaps

    • Systemic diseases (diabetes, liver disease)

    • Perianal neoplasms (Bowen disease and extramammary Paget disease)

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Rule Out

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  • • Perianal neoplasms (Bowen disease and extramammary Paget disease)

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  • • History and physical exam

    • Biopsy and histologic evaluation may be necessary in refractory cases to rule out underlying malignancy

    • Scotch tape test

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  • • Treat identifiable causes of pruritus ani (infection, hemorrhoids, contact dermatitis)

    • Patients should be educated about proper perineal care, and the use of soaps and topical ointments should be discouraged

    • The perineum should be kept dry

    • Alteration in dietary habits may be necessary

    • -Coffee, tea, cola drinks, beer, chocolate, and tomatoes can cause perianal itching and should be excluded from the diet for at least 2 weeks

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