Differentials
Primary cutaneous nocardiosis
SIGNS / SYMPTOMS
Painful skin lesions; may be associated with regional lymphadenopathy and mild systemic symptoms.
INVESTIGATIONS
Demonstration of modified acid-fast organisms on skin lesion smears; culture of skin lesion drainage or biopsy material positive for Nocardia brasiliensis.[36]
Cutaneous Mycobacterium marinum infection
SIGNS / SYMPTOMS
Similar signs and symptoms, although lesions may occasionally be tender; history of acquisition from freshwater or saltwater.[36]
INVESTIGATIONS
Demonstration of acid-fast organisms on skin lesion smears; culture of skin lesion drainage or biopsy material at 32°C (89.6°F) on Lowenstein-Jensen media.
Cutaneous leishmaniasis
SIGNS / SYMPTOMS
No differentiating signs/symptoms from lymphocutaneous sporotrichosis.[36] Travel to endemic areas needed for diagnosis. In the Americas, lymphangitic spread to a proximal skin site is sometimes seen.
INVESTIGATIONS
Polymerase chain reaction of skin biopsy tissue is preferred. Culture from swab of ulcerative lesions on Novy-MacNeal-Nicolle (NNN) medium may be positive for Leishmania.
Ulceroglandular tularaemia
SIGNS / SYMPTOMS
Painful ulcers accompanied by tender regional lymphadenopathy and severe constitutional symptoms; history of contact with infected rabbits or bites from infected arthropods in endemic areas of the northern hemisphere.[36] Short (<1 week) incubation period.
INVESTIGATIONS
Serological testing positive for Francisella tularensis.
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