Skin nontumor
Infestations
Infestations-general
Last author update: 1 June 2016
Last staff update: 21 August 2020
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PubMed Search: Infestations [title]
Table of Contents
Definition / general | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Case reports | Treatment | Differential diagnosisCite this page: Suo L, Nagarajan P. Infestations-general. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorinfestations.html. Accessed December 4th, 2024.
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
- Scabies:
- Polariscopic examination can provide helpful (J Cutan Pathol 2013;40:6)
- KOH preparation from skin scrapings
- Helminths:
- Increased serum eosinophils
- Early serology immunodiagnosis (Parasit Vectors 2015;8:447)
Case reports
- 25 year old woman with subcutaneous human dirofilariasis (Indian J Pathol Microbiol 2015;58:387)
- 37 year old man with subcutaneous cysticercosis (J Dermatol 1998;25:438)
- 50 year old woman with severe pediculosis capitus and related autoeczematization (Dermatol Online J 2016;22:pii 13030)
- 61 year old woman with scabies (N Engl J Med 2016;374:e13)
- 61 year old man with cutaneous Strongyloides infection postchemotherapy (J Cutan Med Surg 2016 Feb 19 [Epub ahead of print])
- Three family members with dermatitis caused by Ornithonyssus bursa (Rev Soc Bras Med Trop 2015;48:786)
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
