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Clinical Summary

Anthrax, a worldwide zoonotic infection caused by Bacillus anthracis, was the 1st definitively recognized bacterial pathogen in human history. Most cases are sporadic, although occasional large outbreaks have been reported in Africa. Control of the disease in livestock has made endemic anthrax uncommon in developed countries, but it has taken on increased importance due to its use as a bioterrorism agent.

Cutaneous anthrax is the most common form, accounting for 95%. Infection occurs after spore exposure, with the initial manifestation of a small, painless, pruritic papule. The papule develops a large, central vesicle, followed by the classic necrotic ulcer with a black, depressed eschar. Local edema, regional lymphadenopathy, and systemic symptoms can occur. About 20% will progress to systemic bacteremia. Inhalational anthrax occurs after aerosolized spore exposure and typically follows a biphasic course: (1) nonspecific upper respiratory infection–like symptoms and (2) then, in 1 to 4 days, fulminant bacteremia with fever, respiratory distress, hemorrhagic mediastinitis, and shock. Gastrointestinal (GI) anthrax is rare, affects the oropharynx or alimentary tract, and occurs after contaminated meat ingestion. It causes a nonspecific gastroenteritis and necrotic GI tract ulcers and may progress to shock or death 2 to 5 days after symptom onset.

FIGURE 21.6

Anthrax. A black eschar with a central hemorrhagic ulceration on the thumb associated with massive edema on the hand. (Used with permission from Wolff K, Johnson RA, Suurmond D. Fitzpatrick’s Color Atlas & Synopsis of Clinical Dermatology. 5th ed. New York, NY: McGraw Hill; 2005:631.)

Management and Disposition

Uncomplicated endemic cutaneous anthrax is typically treated with oral or intramuscular penicillin. Doxycycline, erythromycin, and ciprofloxacin are alternatives. High-dose intravenous (IV) penicillin is used in cutaneous disease with systemic findings and for inhalational or GI disease.

Patients with suspected bioterrorism-related anthrax require hospital admission with immediate public health notification. They should be decontaminated with removal (and sealed storage) of all clothing and cleansing with soap and water. The Centers for Disease Control and Prevention (CDC) guidelines recommend ciprofloxacin or doxycycline as first-line therapy. Inhalational and other severe forms are treated with additional multidrug antimicrobial therapy. Glucocorticoid therapy is controversial but might be beneficial in meningitis or cutaneous disease with extensive head and neck edema.

Pearls

  1. All forms can progress to hemorrhagic meningitis, which can mimic a traumatic tap on lumbar puncture.

  2. Cutaneous and inhalational anthrax have been reported from use of imported animal hide drums.

  3. Injection anthrax is rare and recently found among heroin users in Great Britain and Germany. Symptoms include abscess, cellulitis, necrotizing fasciitis, and sepsis.

  4. The length of antibiotic therapy is usually 7 to 10 days, but postexposure prophylaxis involves 60 days, including vaccine administration.

  5. The classic pathologic finding of inhalational anthrax is hemorrhagic mediastinitis, demonstrated as a widened mediastinum on chest radiography.

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