Scabies_0612 Derm Clinic 1
A previously healthy 9-month-old infant was seen for a rash of three weeks duration. The infant had become increasingly irritable and was feeding poorly. She remained afebrile and had no other associated symptoms. A presumptive diagnosis of impetigo was made, but the eruption failed to respond to topical mupirocin (Bactroban, Centany).
Further questioning revealed that both parents began itching about a month ago after a family trip. Examination revealed inflammatory papules and nodules scattered over the infant’s torso, with a concentration of the lesions in the axillary areas and on the palms.
HOW TO TAKE THE POST-TEST: This Clinical Advisor CME activity consists of 3 articles. To obtain credit, you must also read Asymptomatic red lesions and Pink scaly rash on the trunk and arms; the post-test will include questions related to all three articles.To obtain CME/CE credit, please click here after reading the articles to take the post-test on myCME.com.
Submit your diagnosis to see full explanation.
The diagnosis of scabies was readily made in the office. Material scraped from one of the inflammatory papules was placed on a glass slide, covered with oil and a cover slip, and examined under a microscope; examination revealed several scabitic mites and scybala (feces).
Scabies is a highly pruritic and infectious condition caused by the parasitic mite Sarcoptes scabiei var hominis. The life cycle of a mite is approximately 30 days. Whereas the male mite dies shortly after copulation, the female mite lives on its human (or other animal) host, burrowing into the stratum corneum of the epidermis where she deposits her 60 to 90 eggs. Larvae require only 10 days to mature to adulthood, and the cycle continues.
Scabies is usually transmitted by direct skin-to-skin contact between family members, guests in the home or play in school-aged children. Indirect transmission via such infected fomites as towels, bedsheets or clothing worn by the infested person, although reported, is rare due to the short 24- to 36-hour lifespan of a mite when separated from an animal host.1
The prevalence of scabies in the general population of industrialized countries is low; however, scabies is associated with poverty and overcrowding, primarily among such subgroups as the homeless or displaced children. Outbreaks are more common in winter months in temperate zones due to crowded habitats and the ability of the mite to live longer at lower temperatures when separated from its host.2
The pruritus and rash associated with scabies become clinically apparent approximately three to six weeks after the initial infestation; however, pruritus may develop within 24 to 48 hours with reinfestation. The delay in symptoms is attributed to the time required to develop a type IV hypersensitivity reaction to the mite’s eggs, feces, and saliva.1
Adults typically complain of an itch that intensifies at night; family members or sexual partners often have similar symptoms. Areas most commonly affected in an adult include finger webs, flexor surfaces of wrists and elbows, axillae and external genitalia. The head and neck are spared in immunocompetent adults, although the eruption may be generalized in those with AIDS or individuals residing in nursing homes. Clinically, one most commonly sees linear or serpiginous scaly burrows in body creases of the affected sites.
Scabies is a great imitator in adults and children, and the diagnosis is often overlooked in neonates and infants because of the atypical presentation in this population. Infestations in newborns will not become clinically evident until age 4 to 8 weeks, when a sufficient immune response has developed.3 As opposed to adults, eruptions in infants are often generalized with heavy involvement of the palms, soles, axillae, fingers, face, scalp and even nailbeds.4 The lesions are most commonly pustules, vesicles and occasionally inflammatory nodules. The characteristic short, wavy, linear burrow is typically absent or obscured by an eczematization process.5
The differential diagnosis for scabies in an infant includes eczema, infantile acropustulosis, infantile or neonatal acne or insect bites.1,3,6-8 Atopic eczema is very common in infants and typically presents as a pruritic, relapsing, and remitting rash on the face, posterior scalp, and extensor surfaces of the extremities. Patients often have asthma or a family history of allergies and/or asthma.1,6,9 Secondary eczematization from pruritus-driven scratching can lead to the misdiagnosis of infantile eczema.1
Infantile acropustulosis, a self-limited, acrally distributed, vesiculopustular eruption, can be difficult to distinguish from scabies. In fact, this condition frequently follows a suspected case of scabies and is believed by some to be an “id” reaction to the scabitic mite, although the pathogenesis remains speculative.7,8
Neonatal acne presents within the first few months of life, whereas infantile acne presents after age 3 months; both conditions present as pustules and papules on the infant’s face.3 These are typically minimally pruritic, self-limited eruptions of uncertain etiology, although maternal hormones and genetic predisposition may play pivotal roles.
These dermatoses are frequently treated with topical steroids. Infants with scabies who have been treated with topical steroids often have reduced itching, inflammation, and morphologically altered lesions that can further delay the proper diagnosis and treatment.10,11 Scabies incognito is a term used to describe this phenomenon.
The proper diagnosis usually requires a high index of suspicion.5 A highly specific and sensitive means of diagnosis is not available, leaving examination of scrapings from lesional skin that identify mites, scybala or larvae as the most definitive approach.
If a biopsy is done, the histologic findings may show a female mite burrowed in the epidermis in association with spongiotic edema, vesiculation, hyperkeratosis, and acanthosis.12
For children, the first line of treatment recommended by the CDC is topical 5% permethrin cream applied over the entire body, covering the face, scalp and neck in infants over age 2 months. The cream should be rinsed off after eight to 14 hours, followed by a repeat application one week after the initial treatment. Because of potential neurotoxicity, lindane (Kwell) is no longer recommended for infants.
Other treatment options include topical crotamiton (Eurax), benzyl benzoate and sulfur ointment; these are not considered first-line modalities due to side effects and/or decreased effectiveness when compared with permethrin. Treat all close contacts — including all the members of the household — from the neck down with 5% permethrin to eradicate scabies from the environment and prevent re-infestation.
Such oral therapies as ivermectin (Mectizan , Stromectol) should not be used in children younger than age 5 years.1,2 Towels, linens, clothing and stuffed toys should be washed in hot water or placed in sealed plastic bags for 72 hours.13 Secondary bacterial infections should be treated if present.2 Parents should be advised that pruritus might persist for two to four weeks despite successful treatment.
The patient and family in this case were treated with 5% permethrin cream weekly for two applications. To prevent excessive excoriations, socks were placed over the infant’s hands at night. Symptomatic relief was confirmed two weeks later.
Audrey Vass is a fourth-year medical student at Virginia Commonwealth University School of Medicine in Richmond. Julia R. Nunley, MD, is professor of dermatology at Medical College of Virginia Hospitals, also in Richmond.
2. Heukelbach J, Feldmeier H. “Scabies.” Lancet. 2006;367:1767-1774.
3. Mengesha YM, Bennett ML. “Pustular skin disorders: diagnosis and treatment.” Am J Clin Dermatol. 2002;3:389-400.
4. Paller AS. “Scabies in infants and small children.” Semin Dermatol. 1993;12:3-8.
5. Hurwitz S. “Scabies in babies.” Am J Dis Child. 1973;126:226-228.
6. Fleischer AB Jr. “Diagnosis and management of common dermatoses in children: atopic, seborrheic, and contact dermatitis.” Clin Pediatr (Phila). 2008;47:332-3346.
7. Mancini AJ, Frieden IJ, Paller AS. “Infantile acropustulosis revisited: history of scabies and response to topical corticosteroids.” Pediatr Dermatol. 1998;15:337-341.
8. Humeau S, Bureau B, Litoux P, Stalder JF. “Infantile acropustulosis in six immigrant children.” Pediatr Dermatol. 1995;12:211-214.
9. Krol A, Krafchik B. “The differential diagnosis of atopic dermatitis in childhood.” Dermatol Ther. 2006;19:73-82.
10. Kim KJ, Roh KH, Choi JH et al. “Scabies incognito presenting as urticaria pigmentosa in an infant.” Pediatr Dermatol. 2002;19:409-411.
11. Hengge UR, Currie BJ, Jäger G et al. “Scabies: a ubiquitous neglected skin disease.” Lancet Infect Dis. 2006;6:769-779.
12. Falk ES, Eide TJ. “Histologic and clinical findings in human scabies.” Int J Dermatol. 1981;20:600-605.
All electronic documents accessed June 7, 2012.