Sporotrichosis is an infection caused by Sporothrix schenckii, a fungus that occurs naturally in temperate and tropical locations. Of the two clinical syndromes of sporotrichosis, the subcutaneous and the systemic, the subcutaneous variety is the most common form. The organism is introduced into the skin through a local injury, such as a thorn prick.
Subcutaneous sporotrichosis can present as a lymphatic infection or a fixed infection. The lymphatic form is more common and usually develops on exposed skin sites such as the hands or feet. Days to weeks after dermal inoculation, the infection begins as a nodule that may break down to form a small ulcer. The draining lymphatics become inflamed and swollen and a chain of secondary nodules develops along the course of the lymphatics. These may also break down and ulcerate. The nodules are mildly painful, and systemic symptoms are mild or absent.
In the fixed variety syndrome, the infection remains localized to the one site. A granuloma develops that may ulcerate. Satellite nodules may form around the primary lesion. This form is most common in tropical and subtropical areas.
Differential Diagnosis: Sporotrichosis can be distinguished from cutaneous anthrax in the following manner.
*Primary ulcer or nodule is associated with nodular, tender lymphatic chain to draining regional lymph node
* Patient may be a gardener or have an outdoor occupation
* No vesicular stage
*Ulcer with eschar is painless
* Ulcer and eschar are surrounded by characteristic non-pitting edema
* Lymphatic vessel is not involved
Used with Permission from W.B. Saunders
Color Atlas of Dermatology
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