eMedicine Specialties > Emergency Medicine > Infectious Diseases

Scabies: Differential Diagnoses & Workup

Author: Amy L McCroskey, MD, Resident Physician, Department of Emergency Medicine, Wayne State University Detroit Medical Center, Detroit Receiving Hospital
Coauthor(s): Adam J Rosh, MD, MS, Assistant Professor, Department of Emergency Medicine, Wayne State University/Detroit Receiving Hospital
Contributor Information and Disclosures

Updated: Jul 17, 2009

Differential Diagnoses

Bites, Insects
Categories
Dermatitis, Atopic
Dermatitis, Contact
Psoriasis
Urticaria

Other Problems to Be Considered

Classic scabies

Insect bites
Atopic dermatitis
Contact dermatitis
Psoriasis
Fiberglass exposure
Lichen planus
Dermatitis herpetiformis
Bullous pemphigoid
Urticaria
Chronic lymphocytic leukemia
Necrotizing vasculitis
B-cell lymphoma with monoclonal infiltrate
Eczema

Crusted scabies

Eczema
Psoriasis
Ichthyosis
Adverse drug reactions
Seborrheic dermatitis
Erythroderma
Langerhans cell histiocytosis

Scabies: Classical or Norwegian

Workup

Laboratory Studies

  • Diagnostic testing: Definitive testing relies on the identification of mites, eggs, eggshell fragments, or mite pellets (scybala).3 This is best undertaken by placing a drop of mineral oil directly over the burrow and then scraping longitudinally and laterally across the skin with a scalpel blade. (Avoid causing bleeding.) The sample is placed on a microscope slide and examined under both low and high power. Potassium hydroxide should not be used since it can dissolve mite pellets. Failure to find mites is common and does not rule out the diagnosis of scabies.


Scabies mite. Courtesy of William D. James, MD.

Scabies mite. Courtesy of William D. James, MD.

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Scabies mite. Courtesy of William D. James, MD.

Scabies mite. Courtesy of William D. James, MD.



Scabies mite scraped from a burrow (original magn...

Scabies mite scraped from a burrow (original magnification, 400X). Courtesy of Audra Malerba, DO.

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Scabies mite scraped from a burrow (original magn...

Scabies mite scraped from a burrow (original magnification, 400X). Courtesy of Audra Malerba, DO.


  • Tips on localizing the burrow
    • Applying topical tetracycline to the skin and washing off the excess may reveal burrows. The burrows retain the tetracycline, which fluoresces under a Wood lamp, allowing easy identification.
    • Rubbing a washable felt-tip marker across the suspected site and removing the ink with an alcohol wipe may also localize a burrow more precisely. When a burrow is present, the ink penetrates the stratum corneum and delineates the site.
  • Final diagnosis is based on history, physical examination (burrows), and microscopic examination of mites, eggs, and scybala on mineral oil preparation.

Other Tests

  • Videodermatoscopy or epiluminescence microscopy: Hand-held device magnifies 20-60 times.14
  • DNA amplification by polymerase chain reaction (PCR) followed by enzyme-linked immunosorbent assay (ELISA) are tools also used by some dermatologists in tertiary centers.4 These methods are not readily available in the emergency department or in many dermatology departments.
  • Elevated immunoglobulin E (IgE) titers and eosinophilia may be demonstrated in some patients with scabies.4
  • Skin biopsy
  • Most commonly, scabies is diagnosed clinically based on the appearance and distribution of the rash and the presence of burrows.1
Note: A person can still be infected even if mites, eggs, or fecal matter cannot be identified since fewer than 10-15 mites may be present.1

More on Scabies

Overview: Scabies
Differential Diagnoses & Workup: Scabies
Treatment & Medication: Scabies
Follow-up: Scabies
Multimedia: Scabies
References
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References

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  3. Karthikeyan K. Treatment of scabies: newer perspectives. Postgrad Med J. Jan 2005;81(951):7-11. [Medline].

  4. Chosidow O. Clinical practices. Scabies. N Engl J Med. Apr 20 2006;354(16):1718-27. [Medline].

  5. Feldmeier H, Heukelbach J. Epidermal parasitic skin diseases: a neglected category of poverty-associated plagues. Bull World Health Organ. Feb 2009;87(2):152-9. [Medline].

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  13. Schumann-Gable, N. Dermatology. In: Custer J, Rau R. The Johns Hopkins Hospital:The Harriet Lane Handbook. 8. 18th. Philadelphia, PA: Mosby Elevier; 2009:229-230.

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  17. Fraser V, Elward A. Infection control and isolation recommendations. In: Green G, Harris I, Lin G, Moylan K, eds. The Washington Manual of Medical Therapeutics. 363(9412). ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2004:675.

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  21. Dourmishev AL, Dourmishev LA, Schwartz RA. Ivermectin: pharmacology and application in dermatology. Int J Dermatol. Dec 2005;44(12):981-8. [Medline].

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  24. Fitzpatrick TB, Eisen AZ, Wolff K, et al, eds. Scabies. In: Dermatology in General Medicine. 4th ed. McGraw-Hill: 1993:1812-1813.

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  26. Habif TP. Scabies. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 3rd ed. Mosby-Year Book; 1996:445-53.

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  28. Kabrhel C, Binder W. Clinical pearls: a 37-year-old man with a rash... Acad Emerg Med. Jul 2003;10(7):776-9. [Medline].

  29. Otero L, Varela JA, Espinosa E, et al. Sarcoptes scabiei in a sexually transmitted infections unit: a 15-year study. Sex Transm Dis. Dec 2004;31(12):761-5. [Medline].

  30. Parish LC. Infection control and isolation recommendations. In: Orkin M, Maibach HI, Parish LC, eds. "History of Scabies" in Scabies and Pediculosis. Schwartzman RM: J.B. Lippincott; 1977:675.

  31. Ramos-e-Silva M. Giovan Cosimo Bonomo (1663-1696): discoverer of the etiology of scabies. Int J Dermatol. Aug 1998;37(8):625-30. [Medline].

  32. Schleicher SM, Stewart P. Scabies: The mite that roars. Emerg Med. 1997;6:54-8.

  33. Walton SF, Holt DC, Currie BJ, Kemp DJ. Scabies: new future for a neglected disease. Adv Parasitol. 2004;57:309-76. [Medline].

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Further Reading

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Keywords

scabies, scabies treatment, scabies symptoms, Sarcoptes scabiei var hominis, Norwegian scabies, canine scabies, mange, intense pruritus, nocturnal pruritus, itch mite, 7-year itch, 7 year itch, seven year itch, seven-year itch, mite infestation, skin infestation, scabies causes

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Contributor Information and Disclosures

Author

Amy L McCroskey, MD, Resident Physician, Department of Emergency Medicine, Wayne State University Detroit Medical Center, Detroit Receiving Hospital
Amy L McCroskey, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Medical Student Association/Foundation, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Adam J Rosh, MD, MS, Assistant Professor, Department of Emergency Medicine, Wayne State University/Detroit Receiving Hospital
Adam J Rosh, MD, MS is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

Joseph A Salomone III, MD, EMS Medical Director, Kansas City, Missouri; Associate Professor and Staff Physician, Truman Medical Centers/UMKC School of Medicine
Joseph A Salomone III, MD is a member of the following medical societies: American Academy of Emergency Medicine, National Association of EMS Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Jeter (Jay) Pritchard Taylor III, MD, Compliance Officer, Attending Physician, Emergency Medicine Residency, Department of Emergency Medicine, Palmetto Health Richland, University of South Carolina; Medical Director, Department of Emergency Medicine, Palmetto Health Baptist
Jeter (Jay) Pritchard Taylor III, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Robert E O'Connor, MD, MPH, Professor and Chair, Department of Emergency Medicine, University of Virginia Health System
Robert E O'Connor, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Physician Executives, American Heart Association, American Medical Association, Medical Society of Delaware, National Association of EMS Physicians, Society for Academic Emergency Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.

 
 
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