This often presents as a chronic, slowly progressing nodule or ulcer ("swimming pool granuloma"), lacking the rapid evolution to a black, necrotic eschar seen in cutaneous anthrax.
While related, this infection is extremely rare and typically less virulent, not usually forming the characteristic malignant pustule and eschar of Bacillus anthracis.
This is the classic differential; it is distinguished by a history of a bite, intense initial pain, and a necrotic ulcer that evolves with a more violaceous, ischemic border, often in an irregular shape.
A deep fungal infection would typically have a slower, more indolent course of ulceration, unlike the acute progression from papule to vesicle to necrotic eschar in anthrax.
This is a deeper bacterial infection (usually Strep/Staph) causing a "punched-out" ulcer with a thick crust, but it lacks the hemorrhagic bulla and striking central black eschar of anthrax.
Caused by a poxvirus, this presents as a firm, reddish-purple nodule, often with a central depression, but does not become necrotic or form a black eschar.
Also a poxvirus infection (from sheep/goats), this presents as a large, weeping, reddish nodule, often with a target-like appearance, which is morphologically distinct from the anthrax eschar.
The eschar in rickettsial diseases (like scrub typhus) is typically smaller, less edematous, and accompanied by a more prominent systemic febrile illness with a generalized rash.
