Development of the anthrax carbuncle
The development of the local infectious process begins with the formation of a characteristic "necklace". Secondary vesicles filled with serous or serous-hemorrhagic exudate appear around the primary element of infection. They undergo the same stages of evolution as the main lesion, resulting in the ulcer increasing eccentrically in size over 5–6 days.
At the same time, massive edema spreads from the center to the periphery, involving extensive areas of the body. The skin over the edematous area becomes pale and loses its healthy shine. Upon palpation, the tissues have an elastic or doughy consistency. It is here that a specific diagnostic sign is detected — Stephansky's sign (jelly-like trembling upon percussion with a hammer).
In parallel, the infection involves the lymphatic system: regional lymphangitis and lymphadenitis develop. The more pronounced they are, the more severe the course of the disease.
Eschar formation and healing process
On days 5–8 of the illness, a dense black eschar forms in the center of necrosis, visually resembling a burnt, hard, and often bumpy crust of bread. Beneath this eschar, infiltrate accumulates, raised at the edges by a purple ridge. This picture, resembling a "black coal on a red background," is pathognomonic for anthrax.
The dynamics of recovery are as follows:
- The edema begins to gradually subside from the periphery toward the carbuncle itself.
- After 5–7 days, body temperature drops critically to normal values, and the patient's general condition improves.
- Approximately one week later, the eschar sloughs off. In its place, a crater-like ulcer is exposed with a granulating base and purulent discharge.
- Subsequently, the ulcer becomes covered with a purulent crust. The process of scarring and complete epithelialization takes 2–3 weeks, but can sometimes drag on up to a month and a half.
Severity criteria and prognosis
The severity of cutaneous anthrax depends exclusively on two factors:
- Localization of the primary carbuncle.
- Extent and prevalence of edema.
It is important to remember that neither the size nor the number of the carbuncles themselves affects the severity of the patient's condition. The most unfavorable prognosis and high mortality risk are observed when the lesion is localized on the face: upper lip, chin, or eyelids.
Atypical presentation variants
In addition to the classical carbuncle, the cutaneous form can present in several atypical variants:
- Edematous. The disease manifests with the development of massive, painless, and dense edema without the formation of a visible primary carbuncle. It is accompanied by severe intoxication. Dynamically, the skin undergoes necrosis at the site of edema, and a typical black eschar forms.
- Bullous. Large bullae (blisters) with hemorrhagic contents appear in the area of the infection's entry gate. After 5–10 days, they spontaneously rupture, leaving an extensive necrotic ulceration.
- Erysipeloid. Based on serous inflammation. The skin in the lesion swells and reddens, but remains painless. Numerous whitish vesicles of various sizes with clear fluid form. After they rupture, ulcers are exposed, transforming into an eschar. This is prognostically the most favorable variant (with generalization, mortality does not exceed 1%).
Diagnostic Principles
The clinical diagnosis is based on the presence of sentinel signs: an anthrax carbuncle on exposed skin areas, a black eschar, and an inflammatory ridge. An integral part of diagnostics is a thorough collection of epidemiological history — confirming the patient's contact with infected animals or livestock products as part of their occupational activity.
Briefly: answers to topical questions
With which infectious and purulent-inflammatory diseases is differential diagnosis of the anthrax carbuncle performed?
Differential diagnosis of the anthrax carbuncle is performed with the following infectious and purulent-inflammatory diseases:
- Vulgar furuncles and carbuncles — characterized by significant pain, moderate edema, and purulent inflammation with the formation of a necrotic "core".
- Erysipelas — manifests with bright erythema with blurred borders ("tongues of flame"), pronounced intoxication, and acute onset.
- Plague (cutaneous form) — differs by sharp pain, development of a hemorrhagic carbuncle, and a specific "bubo".
- Tularemia (ulceroglandular form) — the ulcer is smaller (up to 0.5–0.7 cm), with hard raised edges and minimal pain.
Which drugs are the antibiotics of choice for treating cutaneous anthrax?
The antibiotic of choice for etiotropic treatment of anthrax is benzylpenicillin. Until laboratory test results are obtained, patients are empirically prescribed ciprofloxacin. The drug is taken orally at a dosage of 500 mg twice a day; the course of therapy lasts from 7 to 10 days.
What is the anthrax causative agent and what are its pathogenicity factors?
The causative agent of anthrax is the Gram-positive spore-forming bacterium Bacillus anthracis. Virulent strains of B. anthracis form a capsule and produce lethal and edema toxins; pathogenicity is encoded by two plasmids:
- Capsule — consists of D-glutamic acid polymers, prevents phagocytosis, and is encoded by the plasmid pXO2.
- Protective antigen — acts as a carrier: forms channels in the cell membrane through which edema and lethal factors enter the cell.
- Lethal factor — a zinc-dependent protease. As part of the lethal toxin (PA + LF), it causes blood clotting disorders, widespread tissue edema, and septic shock.
- Edema factor — a calcium- and calmodulin-dependent adenylate cyclase. As part of the edema toxin (PA + EF), it increases cAMP production, decreases ATP reserves, disrupts cell membrane permeability, causes edema, and suppresses phagocytic activity.
- Plasmid pXO1 encodes toxin synthesis.
You can remember the appearance of the classical lesion by the visual association: "Black coal on a red background" (it is this appearance that gave the disease its name — anthrax).
Class and exam questions
Does the number of carbuncles on the body affect the severity of the disease?
No. The severity of the disease depends only on the localization of the inflammatory focus and the area of edema spread.
Where are the most dangerous carbuncles located?
The most unfavorable prognosis is observed when the lesion is located on the upper lip, chin, and eyelids. In these cases, the risk of a fatal outcome increases significantly.
Are the rashes painful in cutaneous anthrax?
No, a characteristic feature of anthrax lesions is the absence of pain syndrome in the lesion, despite massive edema and necrosis.
What else to study on this topic
- Pathogenesis of the development of the anthrax carbuncle
- Pulmonary (inhalational) anthrax
- Intestinal form and its clinical variants (intestinal, oropharyngeal)
- Septic form and infectious-toxic shock
- Symptoms and course of hemorrhagic gastroenterocolitis
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