Skin-nontumor / Clinical dermatology
Infestations
General

Author: Liye Suo, M.D. (see Authors page)
Editor: Priya Nagarajan, M.D., Ph.D.

Revised: 28 June 2016, last major update June 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Infestations [title]

Cite this page: Infestations - General. PathologyOutlines.com website. http://pathologyoutlines.com/topic/skinnontumorinfestations.html. Accessed December 4th, 2016.
Definition / General
  • Defined as parasites living in or on a host
  • Skin lesions due to direct irritant effects, immediate or delayed hypersensitivity reaction or specific effects of venom
  • Bites cause skin rash, inflamed papules or nodules, variable ulceration
Epidemiology
  • Scabies: found worldwide and affects people of all races and social classes (CDC website)
    • Highest in endemic areas and in young, elderly, immunocompromised, nursing home residents, and resource poor, overcrowded populations
    • Prevalence ranges from 0.2% to 71.4%, highest in the Pacific and Latin American regions (Lancet Infect Dis 2015;15:960)
Sites
  • Varies depending on infestation

  • Scabies:
    • Most commonly palms, palmar and lateral aspects of fingers, web spaces between fingers, flexor surfaces of wrists, female nipples, and male genitalia

  • Lice:
    • Scalp (Pediculus humanus capitis)
    • Body skin (Pediculus humanus corporis)
    • Hair in the pubic area (Pthirus pubis)

  • Helminths:
    • Subcutaneous areas
Pathophysiology
  • Varies depending on the type of parasite and host response
Etiology
  • Infestation and colonization of susceptible hosts following exposure
  • Arthropod assault or bite
Clinical Features
  • Varies depending on the type of parasite and host response
    • Scabies: burrows, marked pruritus, especially at night
    • Lice: intense itching and irritation, erosion, serous crusting and scaling of the scalp or other areas of the body
    • Helminths: subcutaneous nodules, rashes or ulcer
    • Tungiasis: subcutaneous nodules, rashes or ulcer
  • Extensive on the scalp
  • Can be associated with secondary infections
  • Erosions may progress to become open, non healing wounds and may be associated with secondary infections
  • Systemic symptoms may be present
Diagnosis
  • Physical examination
  • Dermatoscopy is non invasive, important for diagnosis of skin infestation disease (Clin Dermatol 2014;32:315)
  • Histology is useful to find the diagnostic organism
  • PCR or other molecular tests may be performed on skin specimen for specific cases only and are useful in clinically atypical cases (Trends Parasitol 2013;29:35)
Laboratory
Case Reports
Treatment
  • Varies based on type of parasite and host response
  • Goals:
    • Eradicate the parasite: topical or rarely systemic medications or surgical excisions
    • Symptomatic relief: antihistamines and steroids
    • Prevent transmission to close contacts: isolation and treatment of contacts
  • Improving personal hygiene may be helpful
Differential Diagnosis
  • Dermal hypersensitivity reactions to internal antigens such as medications or external antigens including detergents, etc.
  • Lymphomatoid papulosis or other papular dermatoses