eMedicine Specialties > Pediatrics: General Medicine > Dermatology

Scabies

Author: Camila K Janniger, MD, Clinical Professor of Dermatology, Clinical Associate Professor of Pediatrics, Chief of Pediatric Dermatology, New Jersey Medical School
Coauthor(s): Giuseppe Micali, MD, Head, Professor, Department of Dermatology, University of Catania School of Medicine, Italy; Mudra Kumar, MD, MBBS, MRCP, Associate Professor, Department of Pediatrics, University of South Florida College of Medicine
Contributor Information and Disclosures

Updated: May 1, 2009

Introduction

Background

Scabies is a common infestation in the pediatric population caused by the arthropod Sarcoptes scabiei. The mite is transmitted via prolonged direct human contact and rarely by fomites. The adult female mite is 0.3-0.5 mm long and has 4 pairs of legs. The term scabies is believed to be derived from the Latin term scabere, which means to scratch, or possibly from the term scabs, which are secondary to bacterial infection.

In patients with scabies, erythematous vesicles a...

In patients with scabies, erythematous vesicles and papules are present on torso extremities, some with adjacent linear excoriations. Courtesy of Audra Malerba, DO.

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In patients with scabies, erythematous vesicles a...

In patients with scabies, erythematous vesicles and papules are present on torso extremities, some with adjacent linear excoriations. Courtesy of Audra Malerba, DO.


Scabies on hand. Courtesy of William D. James, MD.

Scabies on hand. Courtesy of William D. James, MD.

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Scabies on hand. Courtesy of William D. James, MD.

Scabies on hand. Courtesy of William D. James, MD.


Norwegian scabies. Courtesy of William D. James, ...

Norwegian scabies. Courtesy of William D. James, MD.

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Norwegian scabies. Courtesy of William D. James, ...

Norwegian scabies. Courtesy of William D. James, MD.


Scabies on leg. Courtesy of William D. James, MD.

Scabies on leg. Courtesy of William D. James, MD.

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Scabies on leg. Courtesy of William D. James, MD.

Scabies on leg. Courtesy of William D. James, MD.


Scabies on buttocks. Courtesy of William D. James...

Scabies on buttocks. Courtesy of William D. James, MD.

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Scabies on buttocks. Courtesy of William D. James...

Scabies on buttocks. Courtesy of William D. James, MD.


Scabies on penis. Courtesy of William D. James, M...

Scabies on penis. Courtesy of William D. James, MD.

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Scabies on penis. Courtesy of William D. James, M...

Scabies on penis. Courtesy of William D. James, MD.


Scabies on penis. Courtesy of Hon Pak, MD.

Scabies on penis. Courtesy of Hon Pak, MD.

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Scabies on penis. Courtesy of Hon Pak, MD.

Scabies on penis. Courtesy of Hon Pak, MD.


Pathophysiology

The skin is the main organ involved in scabies. The lesion is caused by the gravid female mite burrowing beneath the stratum corneum. She leaves behind a trail of debris, eggs, and feces (scybala), which induces an immunologic response. The female can lay as many as 90 eggs in her 30-day lifespan. The larvae hatch in 3-4 days; they mature to adult forms over the next 2 weeks and continue the cycle. The average patient is infected with 10-15 live adult female mites at any given time.

Pruritus, the main clinical manifestation, is caused by hypersensitivity to the debris, eggs, and feces, rather than by the direct effects of the mite. The primary lesions appear 3-10 days after exposure to the mite. These lesions include burrows, papules, vesicles, and pustules. The rash usually becomes intensely pruritic several days later because the immune system requires time to mount a hypersensitive response. Nocturnal pruritus is characteristic of scabies infestation. An immunologic study analyzing the cellular infiltrate types and patterns in lesions of scabies concluded that T4 cell dominance is the cause of persistent itching and T8 increase leads to improvement in the pruritus.1

Frequency

United States

Scabies may be observed in people of all ages and is not always a disease of overcrowding. Norwegian (crusted) scabies is observed in patients who are immunocompromised, human immunodeficiency virus (HIV) positive, or institutionalized.

Mortality/Morbidity

Intense pruritus is the major morbidity associated with scabies. This often leads to excoriation and secondary bacterial infection.

Skin disease is among the most frequent causes of morbidity in impoverished sections of Ethiopia; in one study, scabies was the leading cause of hospital admission.2

Race

No racial predisposition to acquiring scabies has been noted.

Age

Scabies can infect people of all age groups from infancy to adulthood.

Clinical

History

  • In scabies, the main presenting symptoms include rash and intense itching.
  • In young infants, pruritus may be difficult to detect. Irritability, especially during sleep, may be the only symptom.
  • A history that includes exposure to other infected family members and contacts is common and helps in establishing the diagnosis.
  • Although most people infected with human T-lymphotropic virus 1 (HTLV-1) remain asymptomatic, they appear to be at increased risk of S scabiei hyperinfection.3 The evaluation for immune deficiency, including infection by HTLV-1 and HTLV-III (HIV-1), may be desirable in patients with Norwegian scabies. 

Physical

  • Primary and secondary lesions
    • The classic scabies rash includes primary and secondary lesions.
    • The primary lesions include burrows, papules, vesicles, and pustules.
    • The secondary lesions occur from scratching and include excoriated papules and crusted areas.
  • Rash distribution
    • In infants, the most commonly affected areas are the palms, soles, axillae, and scalp.
    • Involvement of the face is uncommon in people older than 5 years.
    • In older children and adults, lesions are usually confined below the neck and involve the web spaces between the fingers, flexor surfaces of the arms, wrists, axillae, and the waistline. The umbilicus, nipples, penis, and scrotum may also be affected.
  • Norwegian (crusted) scabies
    • Norwegian scabies is characterized by crusted lesions and scaly plaques located mainly on the hands, feet, scalp, and other pressure-bearing areas. These may sometimes generalize. Hyperkeratosis may occur in these lesions.
    • Nail thickening is typical in patients with crusted scabies.4
    • Patients with Norwegian scabies can be infected with hundreds to millions of adult female mites. As a result, this type of scabies is highly contagious and may spread rapidly through patients in an institutionalized setting.
  • Nodular scabies: Orange-red nodules located in the axillae and groin define nodular scabies. These nodules are pathognomonic of scabies infection.
  • Bullous scabies: Scabies occasionally displays bullae formation that may rarely mimic bullous pemphigoid during clinical and histopathologic examination but not during direct and indirect immunofluorescence examination.5

Causes

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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Further Reading

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Keywords

scabies, itch mite, Sarcoptes scabiei, S scabiei, Norwegian crusted scabies, Norwegian scabies, crusted scabies, pruritus, burrows, papules, vesicles, pustules, nodular scabies, hyperkeratosis, nail thickening, treatment, diagnosis, bullous scabies

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Contributor Information and Disclosures

Author

Camila K Janniger, MD, Clinical Professor of Dermatology, Clinical Associate Professor of Pediatrics, Chief of Pediatric Dermatology, New Jersey Medical School
Camila K Janniger, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

Coauthor(s)

Giuseppe Micali, MD, Head, Professor, Department of Dermatology, University of Catania School of Medicine, Italy
Giuseppe Micali, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

Mudra Kumar, MD, MBBS, MRCP, Associate Professor, Department of Pediatrics, University of South Florida College of Medicine
Mudra Kumar, MD, MBBS, MRCP is a member of the following medical societies: American Academy of Pediatrics and American Society of Hematology
Disclosure: Nothing to disclose.

Medical Editor

Kevin P Connelly, DO, Clinical Assistant Professor, Department of Pediatrics, Division of General Pediatrics and Emergency Care, Virginia Commonwealth University; Medical Director, Paws for Health Pet Visitation Program of the Richmond SPCA; Pediatric Emergency Physician, Emergency Consultants Inc, Chippenham Medical Center
Kevin P Connelly, DO is a member of the following medical societies: American Academy of Pediatrics, American College of Osteopathic Pediatricians, and American Osteopathic Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Robert A Schwartz, MD, MPH, Professor and Head, Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Robert A Schwartz, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and Sigma Xi
Disclosure: Nothing to disclose.

CME Editor

Merrily P M Poth, MD, Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences
Merrily P M Poth, MD is a member of the following medical societies: American Academy of Pediatrics, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society
Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

 
 
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