Scabies (pediatric) - Anogenital in
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Synopsis
Scabies is an ectoparasitic infestation caused by the mite Sarcoptes scabiei variety hominis. Scabies is most common in young children, and the highest prevalence is seen in children aged younger than 2 years. Scabies is transmitted by direct skin-to-skin contact and very rarely by indirect route through infected bedding, clothing, or other fomites.
The average number of adult female mites in an infested individual is 10-15. The mite lives in burrowed tunnels within the human epidermis. Female mites lay eggs in these burrows, and larvae emerge after about 3 weeks. If separated from human hosts, the mite can survive at most a few days.
Scabies affects all ethnic groups and socioeconomic levels. Frequent outbreaks are common in schools, group homes, and orphanages where direct contact with infested individuals is common. The predisposing factors are overcrowding, poverty, poor nutrition, poor hygiene, and being undomiciled. Other predisposing conditions include immunocompromise, human immunodeficiency virus (HIV) infection, and severe intellectual or physical disability. These groups are more likely to have crusted (or Norwegian) scabies, which presents as itchy, scaly, thick papules and plaques that can be local or generalized. These lesions may mimic eczema, psoriasis, warts, or a drug reaction, and nail dystrophy can be present. It is extremely contagious due to the high mite burden that can number in the thousands.
Pruritus is a hallmark of scabies, and a variety of primary and secondary skin lesions occur. Scabies infection may be complicated by id reactions and secondary bacterial infections with both Streptococcus and Staphylococcus.
Codes
ICD10CM:B86 – Scabies
SNOMEDCT:
128869009 – Infestation by Sarcoptes scabiei var hominis
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Differential Diagnosis & Pitfalls
- Papular urticaria – A hypersensitivity reaction to a variety of bites, such as mosquitoes, fleas, bedbugs, and mites. There may be a seasonal occurrence. Recurrent episodes of excoriated papular and urticarial lesions on the exposed parts of the extremities (extensor aspect) are the cardinal features. Absence of burrows and family history of itching differentiate this from scabies.
- Atopic dermatitis – Eczematous lesions with oozing on the face and flexural areas (cubital and popliteal fossa). Lichenification is seen in chronic dermatitis. Burrows are absent, and lesions are not seen in the web spaces.
- Impetigo – Erythematous vesiculopustular lesions that rupture, forming the pathognomonic honey-colored crust. Lesions may involve the face, neck, and extremities. Scabies may sometimes be impetiginized, so a good history may distinguish primary versus secondary impetigo.
- Erythema toxicum neonatorum – Appears in the first 2-4 days of life and spontaneously resolves within hours to days. Tzanck smear from a pustule reveals numerous eosinophils.
- Transient neonatal pustular melanosis – Presents at birth with fragile pustules and hyperpigmented macules. Pustules spontaneously resolve within 2 weeks.
- Neonatal herpes – Discrete or grouped vesicles on an erythematous base, possibly with systemic symptoms. Tzanck smear from the vesicle reveals multinucleated giant cells.
- Congenital cutaneous candidiasis – Presents at birth, may affect the nails, may be associated with placental lesions and inflammation. Potassium hydroxide (KOH) preparation of vesicular contents reveals yeast and pseudohyphae.
- Cutaneous candidiasis – Affects the intertriginous areas, especially the groin or neck, in the form of confluent erythematous patches with multiple small satellite pustules. KOH test from a pustular lesion reveals budding spores and pseudohyphae.
- Folliculitis
- Nummular dermatitis
- Langerhans cell histiocytosis, insect bites, tinea corporis, dermatitis herpetiformis, eczema herpeticum, pityriasis rosea, and viral exanthems
- Leukemia or lymphoma cutis, prurigo nodularis (differential for scabies nodules)
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Last Reviewed:02/26/2018
Last Updated:06/16/2021
Last Updated:06/16/2021
Scabies (pediatric) - Anogenital in
See also in: Overview