Cutaneous anthrax is one of 4 major syndromes caused by Bacillus anthracis, an encapsulated, gram-positive, spore-forming bacillus. The other "forms" are inhalational, gastrointestinal, and injection anthrax. Bacillus anthracis has been classified by the US Centers for Disease Control and Prevention (CDC) as a Category A bioterrorism agent. If anthrax were to be intentionally dispersed, the most likely syndromes will be inhalational and cutaneous. Cutaneous anthrax occurs in endemic areas (eg, Turkey) due to exposure to infected animals. Cases of cutaneous anthrax also occurred during the intentional exposures in the United States in 2001.

Bacillus anthracis is present in both domestic and wild animals throughout the world (mainly in agricultural regions of South and Central America, Southern and Eastern Europe, Asia, Africa, the Caribbean, and the Middle East) and can be transmitted by these animals' meat, wool, or hides. Therefore, veterinarians and those in the meat-, wool-, or hide-processing industries, as well as those who have butchered meat or touched raw meat, may develop cutaneous lesions.

Bacillus anthracis is not routinely found in all US soil, although it can be found in soil where previously infected animals have died. Major epizootics in the past have occurred in North Dakota, South Dakota, Minnesota, and Texas. Hence, international travel should be elicited when evaluating a suspect lesion.

Cutaneous anthrax lesions evolve from nonpainful, pruritic papules to clusters of vesicles to ulcers within 1-2 days following exposure of abraded skin or wounds to the spores. The ulcers then develop into depressed, black eschars over the next 2-5 days. The most common areas affected are the arms, face, and neck. Some lesions may have extensive edema formation. The incubation period is 1-12 days.

Cutaneous anthrax may involve the eyelids. On the periorbital skin, the disease follows its typical progression, with edema and pruritic papules giving way to bulla and subsequent eschar formation. Sequelae include ectropion, lagophthalmos, uveitis, and corneal scarring. Cutaneous anthrax may be confused with preseptal or orbital cellulitis. The presence of vesicles/bullae with resultant eschar formation are important clues.

With antibiotic treatment, the mortality rate for cutaneous anthrax is approximately 1%. However, without treatment, it may progress to a systemic form of anthrax with a mortality rate of approximately 20%. In these cases, the spores introduced into the body are eaten by macrophages and taken to regional lymph nodes, where they germinate into bacteria. Released into the lymph system, they enter the blood stream, causing septicemia-releasing toxins that result in a fatal toxemia.