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A 5-month-old Hispanic infant presents for evaluation of a rash involving his arms and trunk that has worsened over the past month. The parents report that his 2-year-old brother is similarly affected. Neither boy has responded to topical 1% hydrocortisone cream. Both parents are without rash and deny itching. Physical examination of the infant reveals scattered erythematous papules and vesiculopustules.
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Scabies is a contagious skin disease caused by Sarcoptes scabiei, a mite that is invisible to the naked eye.1 Endemic in poor tropical countries, the worldwide incidence is estimated to be 300 million new cases each year with 1 million cases occurring annually in the United States.2 The condition is contagious and spreads by direct contact; facilities such as nursing homes and prisons are common breeding grounds.
Scabies initially presents with excoriated papules and erythematous patches. The hallmark symptom of scabies is severe itching that often interferes with sleep. Itching is the result of a hypersensitivity reaction to mites and their feces and may take weeks after initial infestation to manifest.3 Areas of involvement often include the finger webs, buttocks, scrotum, and under the breasts.
Under a dermatoscope, the head and forelegs of the mite form a triangular shape that looks like a hang-glideror stealth bomber.4,5 Diagnosis is made by visualization of the mite under a microscope, although many cases are treated empirically.
Scabies in infants and young children characteristically involves the face, scalp, palms, and soles.6 Lesions may be papules, vesiculopustules, and nodules; burrows are usually not visualized. The treatment of choice is permethrin, which is well-tolerated and safe.7 Scabies resistance to permethrin therapy has been report and is on the rise.8
Brittany Spinosa-Weber, PA-C, is a physician assistant at the DermDox Dermatology Centers in Leola, Pennsylvania. Stephen Schleicher, MD, is director of the DermDox Dermatology Centers in Pennsylvania, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Chosidow O. Clinical practices. Scabies. N Engl J Med. 2006;354(16):1718-1727. doi:10.1056/NEJMcp052784
2. Stanford University. Scabies. Accessed September 14, 2021. https://web.stanford.edu/group/parasites/ParaSites2005/Scabies/SCABIES.html
3. Mellanby K. The development of symptoms, parasitic infection and immunity in human scabies. Parasitology. 2009;35(4):197-206. doi:10.1017/S0031182000021612
4. Neynaber S, Wolff H. Diagnosis of scabies in dermatology. CMAJ. 2008;178(12):1540-1541. doi.org/10.1503/cmaj.061753
5. Fox G. Diagnosis of scabies by dermoscopy. BMJ Case Rep. 2009:bcr06.2008.0279. doi:10.1136/bcr.06.2008.0279
6. Paller AS. Scabies in infants and small children. Semin Dermatol. 1993;12(1):3-8.
7. Hoffmann JC, Mößner R, Schön MP, Lippert U. Topical scabies therapy with permethrin is effective and well tolerated in infants younger than two months. J Dtsch Dermatol Ges. 2019;17(6):597-600. doi:10.1111/ddg.13854
8. Meyersburg D, Kaiser A, Bauer JW. Loss of efficacy of topical 5% permethrin for treating scabies: an Austrian single-center study. J Dermatolog Treat. Published online: June 4, 2020. doi:10.1080/09546634.2020.1774489
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