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Skin-nontumor

Infectious disorders

Anthrax

Reviewer: Cecilia Rosales, M.D., Baylor College (see Reviewers page)
Revised: 24 August 2011, last major update July 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Definition
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● “Coal” in Greek; refers to black coloration of skin eschar

Etiology
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● An uncommon, cutaneous infection due to endospores of Bacillus anthracis, a common soil organism, which typically causes illnesses in animals

Clinical features
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● Causes cutaneous, pulmonary or gastrointestinal symptoms
● Cutaneous anthrax is marked by a boil-like lesion that eventually forms an ulcer with a black center
● 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

Treatment
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● The cutaneous form of anthrax responds well to several antibiotics
● With treatment, complete recovery from cutaneous anthrax is usual
● Antibiotics reduce mortality from 20% to less than 1%

Case reports
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● 51 year old woman with localized skin ulceration and prominent edema of forehead, cultured negative for B. anthracis (Arch Pathol Lab Med 2004;128:709)

Clinical images
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Cutaneous lesion with eschar

Micro description
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● Eschar shows coagulative necrosis of superificial epidermis and dermis, with prominent edema of underlying viable dermis, frequent focal hemorrhages, intense, reactive-appearing mononuclear inflammatory infiltrates around small vessels and some adnexae
● 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

Micro images
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Figure 1: coagulative necrosis of superficial epidermis and dermis, edema of underlying viable dermis, frequent focal hemorrhage, intense mononuclear inflammation around small vessels and some adnexa
Figure 2: sharp demarcation between superficial necrotic and deeper edematous viable tissue, with occasional islands of regenerating epidermis present under necrotic eschar
Figure 3: mononuclear infiltrate


Bacteria

Additional references
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● Centers for Disease Control

End of Skin-nontumor > Infectious disorders > Anthrax

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