Skin nontumor

Infectious disorders

Anthrax



Topic Completed: 1 July 2016

Minor changes: 17 August 2020

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Anthrax [title] skin

Abha Soni, D.O., M.P.H.
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Cite this page: Soni A. Anthrax. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumoranthrax.html. Accessed December 2nd, 2021.
Definition / general
  • "Coal" in Greek; refers to black coloration of skin eschar
Epidemiology
  • 2,000 cases per year worldwide - 95% are skin infections
Etiology
  • An uncommon, cutaneous infection due to endospores of Bacillus anthracis, a common soil organism, which typically causes illnesses in animals
  • Exposure is through breathing, eating and exposed cuts in skin
Clinical features
  • Causes cutaneous, pulmonary or gastrointestinal symptoms
  • Cutaneous anthrax is marked by a boil-like lesion that eventually forms an ulcer with a black center (eschar)
  • Culture: nonhemolytic, nonmotile and ground glass colonies that retain their shape when manipulated; grows readily on sheep red blood cell agar (no special conditions needed)
  • Gram stain: gram positive, spore forming rods
Diagnosis
  • Blood, skin, spinal fluid or respiratory secretions are collected for testing
  • Organisms are gram positive
  • PCR and Immunofluorescence useful for confirmation
  • Xray and CT scans recommended to confirm mediastinal widening / pleural effusions in inhalation anthrax
Case reports
Treatment
  • The cutaneous form of anthrax responds well to several antibiotics; with treatment, complete recovery is usual
  • Antibiotics reduce mortality from 20% to less than 1%
Microscopic (histologic) description
  • Eschar shows coagulative necrosis of superficial epidermis and dermis, with prominent edema of underlying viable dermis, frequent focal hemorrhages, intense, reactive appearing mononuclear inflammatory infiltrates around small vessels and some adnexal structures
  • Neutrophils only around necrotizing sebaceous glands
  • Sharp demarcation between superficial, necrotic and deeper edematous viable tissue (at periphery); occasional islands of regenerating epidermis under necrotic layer of eschar
  • Vessels with degenerated endothelial cells and focal thrombi
  • No abscess
  • No granulation tissue
Positive stains
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