Anthrax, Cutaneous
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Diagnosis Synopsis
Cutaneous anthrax is a bacterial infection caused by Bacillus anthracis, an encapsulated, gram-positive, spore-forming bacillus. Although inhalational and gastrointestinal forms of anthrax exist, approximately 95% of all anthrax cases are cutaneous.

B. anthracis has been classified by the CDC as a Category A bioterrorism agent due to its high lethality, hardiness, and ease of weaponization. The spores, which are resistant to heat, UV light, microwave radiation, and many otherwise useful disinfectants, can remain dormant in soil for years. If anthrax were to be weaponized, the most likely method of dispersal would be by aerosol release. The identification of patients with cutaneous anthrax may be the first evidence of an anthrax attack.

Prior to 2001, there had not been a case of cutaneous anthrax reported in the United States since 1992. There were 11 cases of cutaneous anthrax attributed to the terrorist events of 2001 (7 confirmed, 4 suspected). Cutaneous anthrax should be considered in postal workers and those who handle mail or packages when the patient presentation includes localized vesicles, bullae, or eschars.

The incubation period is between 12 hours and 7 days, but it averages 3 days. Cutaneous anthrax lesions evolve from pruritic papules to clusters of vesicles. Commonly, the lesions involve the exposed areas of the hands, neck, and arm and appear as an insect bite or pimple. Vesicles are initially clear and become blue to black within the third to fourth day. The painless black eschar appears by the fifth to seventh day. "Malignant edema," a rare and severe local reaction, usually involves the face and neck. Generally, patients have few symptoms, such as malaise and low-grade fever. Blood cultures are often sterile.

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.

B. 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 their meat, wool, or hides. Therefore, veterinarians and those in the meat-, wool-, or hide-processing industries are the most at risk for contracting naturally occurring cutaneous anthrax. Cutaneous anthrax can also be acquired during the sacrifice of infected animals such as sheep, goats, cattle, water buffalo, antelopes, elephants, giraffes, and zebras. Anthrax is rarely found in animals in the US. B. 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 ND, SD, MN, and TX.

In 2002, the United States Department of Defense reintroduced the vaccination of military personnel and essential emergency civilians against anthrax.

Look For
Look for an initial pruritic macule or papule that enlarges into a plaque. Vesicles in a group or ring then appear, sometimes coalescing into bullae. They can discharge clear to serosanguineous fluid, with numerous organisms seen on Gram stain. A painless, depressed, black eschar develops at the center with extensive local edema. The eschar loosens and falls off in 2-3 weeks, leaving no permanent scar. Lymphangitis and painful lymphadenopathy are common.

Medical Disclaimer:
The information contained in this Web page is intended to be an adjunct to traditional medical information sources. It is not intended to be a substitute for professional medical judgment.

Authors and Editors:
Alex Garza, MD