Clinical History
The patient is a 57-year old handyman who presented one day after believing he had been bitten by an
arthropod after working in a ventilation tower. The following day he collapsed and was noted to have a
necrotic lesion on his chest in the approximate area of his alleged bite the day before. This lesion was
biopsied.
Case 2 - Figure 1 - Scanning magnification shows massive dermal edema.
|
Case 2 - Figure 2 - High-power magnification shows mixed acute and chronic inflammation, numerous extravasated red blood cells, and fibrin thrombi in small vessels.
|
This case was kindly provided by provided by Dr. PH McKee, Boston.
Anthrax
Anthrax is caused by a gram-positive rod-shaped non-motile bacterium, bacillus
anthracis. Spores form when the bacteria are exposed to ambient air and are resistant to heating
and other adverse conditions; anthrax has been successfully cultured from a 50-year old desiccated
culture.
Anthrax is disease of wild animals and livestock. Animals are infected from eating spore-laden plant
material and soil, and drinking from contaminated waterholes. Sporulation and, consequently, infection
are promoted in areas characterized by alternating drought and rainy periods.
Humans may contract the disease following exposure to animals or animal products, especially animal
hides; the appellation Woolsorter's disease is sometimes applied to inhalation anthrax. In most parts of
the world the incidence of the infection in animals is waning, but 10,000 cases were reported in Africa
in the early 1980s. In recent years up to 2001, anthrax infection in humans has been largely in the form
of sporadic cases, usually workers handling animal hair. In 1979, 96 cases (77 inhalational) of anthrax
resulting in 64 deaths after the accidental release of organisms from a military facility in Sverdlovsk
(now Ekaterinburg), Russia. Most cases were caused by inhalation of spores and the high death rate
underscores the frightening potential of anthrax as a bioweapon. In 1987, twenty-five patients in
Paraguay developed anthrax from exposure to a single infected cow.
Three forms of human anthrax infection- cutaneous, inhalation, and gastrointestinal- are recognized.
The vast majority of infections are of the cutaneous form. Lesions occur at sites where spores come in
contact with cutaneous cuts or abrasions, usually within 7-10 days of exposure. Rarely, lesions occur
following the bite of an insect that has fed on anthrax-infected animal carcasses. Cutaneous infection
begins as a small papule. Lesions turn blue to black and tend to blister, ulcerate and form a black
eschar (the term "anthrax" is a Latin transliteration of the Greek word meaning coal). Cellulitis and
lymphadenopathy are features in some patients. If left untreated, 10-20% of patients succumbs to the
disease.
Biopsies of cutaneous anthrax are characterized by dermal edema associated with a neutrophil-rich
inflammatory infiltrate. Depending on the stage in evolution of the lesion, ulceration or a blister may
be present. Elongate gram-positive rods are seen in gram stained sections.
Gastrointestinal anthrax, an extremely rare form of the disease is acquired by eating contaminated
meat that is raw or undercooked. Most reported cases have occurred in Asia and Africa and detailed
clinicopathologic information on this form is lacking. Initial manifestations include nausea, vomiting,
fever, and abdominal pain. Within a few days of exposure, patients develop bloody diarrhea and shock.
Most patients with gastrointestinal infection die; however, rare patients have survived. Occasionally
patients may develop lesions in the oropharynx.
Inhalation anthrax was a rare form of the disease: eighteen cases were reported between 1900 and
1980 in the U.S. There was not a single case of inhalation anthrax in the United States between 1981 and
2001. One to 5 days following inhalation of spores, patients develop cough, chest pain, and dyspnea.
Stridor, respiratory failure, cyanosis, and shock occur within a few days of initial symptoms.
Mediastinal edema is a characteristic radiologic finding. Hemmorhagic meningitis is seen in many
patients.
Illness is promoted by several virulence factors. The negative charged capsule composed of
poly-D-glutamic acid inhibits phagocytosis. Exotoxins are responsible for edema and death.
The World Health Organization estimates that release of 50 kg of anthrax spores upwind of a city of
500,000 would infect 125,000 people and kill 95,000. No other known biologic agent could produce such a
devastating toll so quickly. For this reason, anthrax is considered by many to be the single greatest
biologic warfare threat. In 2001, anthrax-laden letters caused 22 cases of anthrax (11 inhalational; 11
cutaneous) and resulted in 5 deaths.
Treatment is aimed at controlling infection and supporting the patient against physiologic effects of
anthrax toxins. Prompt antibiotic therapy is critical in all patients with anthrax. Individuals with
known exposure should be given a prophylactic course of antibiotics in addition to vaccination to prevent
latent infection.
References
- Sen SK, Minett FC. Experiments on the transmission of anthrax through flies. Ind J Vet Sci An Husb 1944;14:149-158.
- Dutz W, Kohout E. Anthrax. Pathol Ann 1971;6:209-248.
- Sirisanthana T, Brown AE. Anthrax of the gastrointestinal tract. Emerg Infec Dis 2002;8:649-651.
- Nalin DR, Sultana b, Sahunja R, et al. Survival of a patient with intestinal anthrax. Am J Med 1977;62:130-132.
- Brachman PS. Inhalation anthrax. Ann New York Acad Sci 1980;353:83-93.
- Abramova FA, Grinberg LM, Yampolskaya OV, Walker DH. Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1970.
- McGovern TW, Christopher GW, Eitzen EM. Cutaneous manifestations of biological warfare and related threat agents. Arch Derm 1999;135:311-322.
- Report of a WHO group of consultants. Health aspects of chemical and biological weapons. Geneva. World Health Organization; 1970. p. 97-99.
- Dixon TC, Meselson M, Guillemin J, Hanna PC. Anthrax. NEJM 1999;341:815-826.
- The CDC has an excellent website: www.cdc.gov
- The AFIP also has an excellent website: www.afip.org
