Red All Over
Answer: D
This infant is suffering from generalized scabies. In adults, the distribution is classically in the interdigital space of the hands and feet, but may present as secondary sites in the axillae, groin, or abdomen. The diagnosis in infants is less typical: lesions may be only mildly erythematous, more amorphous, and not in the stereotypical areas – the rash is often generalized.
A review of scabies:
● The mite Sarcoptes scabei [Gr., sarca – flesh + koptein – to gnaw, to cut into] is highly contagious and
can survive off a host for up to two days.
● The female mite causes the clinical manifestations of intense pruritus by burrowing into the skin at 2 mm/day,
laying eggs as she goes; larvae hatch in 3-4 days, leave the burrow to surface, copulate amongst themselves,
then the fertilized females burrow back in to feed and hatch.
● Mites can jump-crawl on the surface of the skin at 3 cm per minute.
● Symptoms begin usually a few weeks after the primary infestation, as the mites settle in and the host immune
response mounts.
● For those who have been previously infected, symptoms begin within 1-3 days, as these people have been
sensitized.
Classically burrows (if found) are greyish-brown to red. Unfortunately in both adults and children, these tell-tale signs of scabies may be altered by excoriation or superinfection.
In infants, the most common presenting lesions are papules, vesiculopustules, and nodules, making the diagnosis sometimes less clear.
This infant is suffering from generalized scabies. In adults, the distribution is classically in the interdigital space of the hands and feet, but may present as secondary sites in the axillae, groin, or abdomen. The diagnosis in infants is less typical: lesions may be only mildly erythematous, more amorphous, and not in the stereotypical areas – the rash is often generalized.
A review of scabies:
● The mite Sarcoptes scabei [Gr., sarca – flesh + koptein – to gnaw, to cut into] is highly contagious and
can survive off a host for up to two days.
● The female mite causes the clinical manifestations of intense pruritus by burrowing into the skin at 2 mm/day,
laying eggs as she goes; larvae hatch in 3-4 days, leave the burrow to surface, copulate amongst themselves,
then the fertilized females burrow back in to feed and hatch.
● Mites can jump-crawl on the surface of the skin at 3 cm per minute.
● Symptoms begin usually a few weeks after the primary infestation, as the mites settle in and the host immune
response mounts.
● For those who have been previously infected, symptoms begin within 1-3 days, as these people have been
sensitized.
Classically burrows (if found) are greyish-brown to red. Unfortunately in both adults and children, these tell-tale signs of scabies may be altered by excoriation or superinfection.
In infants, the most common presenting lesions are papules, vesiculopustules, and nodules, making the diagnosis sometimes less clear.
Eliciting a history of symptomatic close contacts (human or animal) is imperative, as the contagious nature of scabies requires some contact or proximity (via direct infection or fomites). Luckily, tracking the whereabouts and contacts in infants is an easier prospect than in adolescents and adults.
Permethrin 5% cream is a safe and effective treatment: parents are instructed to wash all sheets and clothes
in the home in hot water (or bag bulky items and keep sealed for two weeks) and apply the cream head to toe and leave on overnight and wash in the morning. Permethrin has a 95-98% success rate. It may be reapplied in 1-2 weeks if there is incomplete effect. It should be noted, however, that pruritus may continue for several days after treatment, as the mites die and expose the host’s immune system to ongoing triggers.
Due to the messiness of permethrin treatment, ivermectin as a one-time PO dose may be elected in older children and adults; however, its success rate is reported to be only 70%. A recent observational study showed that when ivermectin PO was repeated two weeks after the initial dose, the success rate was similar to one-dose topical permethrin. This may be a viable option in the adolescent or adult with an insecure social situation or address, for whom an overnight permethrin treatment and a morning shower are problematic. (Note: ivermectin is contraindicated in lactating women and children less than 15 kg.)
Ivermectin PO is used in conjunction with topical permethrin in crusted scabies (so-called Norwegian scabies, due to its first mention in fin-de-siècle Norwegian leper colony). This highly contagious form of scabies bears special note: although it is caused by the same mite, the patches are teeming with thousands of mites (in contrast to typical scabies where there are usually no more than 60-100). Often seen in elderly, those with Down syndrome, or the immunocompromised, crusted (Norwegian) scabies is effortlessly transmitted (patients must be isolated) and presents as an often non-pruritic malodorous crust-scale and can be devastating:
Permethrin 5% cream is a safe and effective treatment: parents are instructed to wash all sheets and clothes
in the home in hot water (or bag bulky items and keep sealed for two weeks) and apply the cream head to toe and leave on overnight and wash in the morning. Permethrin has a 95-98% success rate. It may be reapplied in 1-2 weeks if there is incomplete effect. It should be noted, however, that pruritus may continue for several days after treatment, as the mites die and expose the host’s immune system to ongoing triggers.
Due to the messiness of permethrin treatment, ivermectin as a one-time PO dose may be elected in older children and adults; however, its success rate is reported to be only 70%. A recent observational study showed that when ivermectin PO was repeated two weeks after the initial dose, the success rate was similar to one-dose topical permethrin. This may be a viable option in the adolescent or adult with an insecure social situation or address, for whom an overnight permethrin treatment and a morning shower are problematic. (Note: ivermectin is contraindicated in lactating women and children less than 15 kg.)
Ivermectin PO is used in conjunction with topical permethrin in crusted scabies (so-called Norwegian scabies, due to its first mention in fin-de-siècle Norwegian leper colony). This highly contagious form of scabies bears special note: although it is caused by the same mite, the patches are teeming with thousands of mites (in contrast to typical scabies where there are usually no more than 60-100). Often seen in elderly, those with Down syndrome, or the immunocompromised, crusted (Norwegian) scabies is effortlessly transmitted (patients must be isolated) and presents as an often non-pruritic malodorous crust-scale and can be devastating:
Although scabies is a clinical diagnosis, in the less-than-clear cases skin scrapings can be put under mineral oil under a microscope to confirm the presence of mites. In children and in adults who cannot tolerate skin scraping, the adhesive test can be used: adhesive tape is firmly pressed up against a suspect lesion, pulled off quickly, and the adhesive side is applied to a microscope slide.
Urticaria (A) in children shares some qualities with scabies: it is pruritic, amorphic, and raised. Pattern recognition and history are helpful to distinguish them: acute onset, waxing/waning/migrating rash, and lack of contacts with the same argues for urticaria and against scabies.
Drug eruption (B) may share many of the same characteristics of scabies and urticaria, but has a distinct appearance, is often blanching, and a history of a trigger that is suggestive.
Eczema (C) is often misdiagnosed in cases of scabies. A thorough history and physical exam (including tempo of disease and subtle differences in lesions) helps to separate the two. When in doubt, permethrin is a safe drug to give as a diagnostic and therapeutic agent in selected patients (despite the hassle and disruption that scabies treatment conveys).
Bottom line:
Scabies in infants and young children can be less straightforward than in adults for a variety of
reasons:
● The rash is often generalized
● Lesions may be pustular, vesicular, or nodular
● Lesions may be less inflamed than in adults (possibly as this is the infant’s first exposure to scabies)
References
American Academy of Pediatrics. Scabies. In: Pickering LK, ed. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003.
Chosidow O. Scabies. N Engl J Med. 2006; 354:1718-1727
Currie BJ, McCarthy JS. Permethrin and Ivermectin for Scabies. N Engl J Med. 2010; 362:717-725
Paller AS. Scabies in infants and small children. Semin Dermatol. 1993 Mar;12(1):3-8.
Steen CJ, Carbonaro PA, Schwartz RA. Arthropods in dermatology. J Am Acad Dermatol 2004; 50: 819-42.
Walton SF, Currie BJ. Problems in Diagnosing Scabies, a Global Disease in Human and Animal Populations. Clin Microbiol Rev. 2007; 20(2): 268–27.
Urticaria (A) in children shares some qualities with scabies: it is pruritic, amorphic, and raised. Pattern recognition and history are helpful to distinguish them: acute onset, waxing/waning/migrating rash, and lack of contacts with the same argues for urticaria and against scabies.
Drug eruption (B) may share many of the same characteristics of scabies and urticaria, but has a distinct appearance, is often blanching, and a history of a trigger that is suggestive.
Eczema (C) is often misdiagnosed in cases of scabies. A thorough history and physical exam (including tempo of disease and subtle differences in lesions) helps to separate the two. When in doubt, permethrin is a safe drug to give as a diagnostic and therapeutic agent in selected patients (despite the hassle and disruption that scabies treatment conveys).
Bottom line:
Scabies in infants and young children can be less straightforward than in adults for a variety of
reasons:
● The rash is often generalized
● Lesions may be pustular, vesicular, or nodular
● Lesions may be less inflamed than in adults (possibly as this is the infant’s first exposure to scabies)
References
American Academy of Pediatrics. Scabies. In: Pickering LK, ed. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003.
Chosidow O. Scabies. N Engl J Med. 2006; 354:1718-1727
Currie BJ, McCarthy JS. Permethrin and Ivermectin for Scabies. N Engl J Med. 2010; 362:717-725
Paller AS. Scabies in infants and small children. Semin Dermatol. 1993 Mar;12(1):3-8.
Steen CJ, Carbonaro PA, Schwartz RA. Arthropods in dermatology. J Am Acad Dermatol 2004; 50: 819-42.
Walton SF, Currie BJ. Problems in Diagnosing Scabies, a Global Disease in Human and Animal Populations. Clin Microbiol Rev. 2007; 20(2): 268–27.