Sporothrix schenckii is a dimorphic fungus that is present in the soil, and is often found in living organisms, such as rose thorns, or in decomposing plant matter, such as peat moss.
Sporothrix schenckii can exist as one of two morphologies, and it is referred to as a thermally dimorphic fungi, as it grows as a mold at 25 degrees C, but as a yeast at 37 degrees C. In its moldy, or hyphal form, it grows as velvety, white colonies. Meanwhile, when in host tissues, or in labs at 37 degrees C, it grows in its yeast form, which resembles an elongated cigar.
The classic description of this organism is that it appears as a cigar-shaped budding yeast on microscopy.
These fungi can be found on living plant tissue, and often, this organism is traumatically introduced into the host tissue via a rose thorn prick, hence the pseudonym “rose gardener’s disease.” Once introduced into the skin, Sporothrix schenckii infections initially manifest as a local pustule or ulceration at the site of trauma.
Another reservoir for encountering Sporothrix schenckii is peat moss, which is the partially decomposed remains of formerly living moss. In addition to rose thorn pricks, those with open wounds that come in contact with peat moss can potentially develop sporotrichosis.
When these fungi are introduced into the body via disruption of the skin, patients initially display small lesions. These manifest as local pustules, or ulcerations surrounded by erythema at the location of the thorn prick.
Once introduced into the body, infection spreads through the lymph along lymphatic vessels, resulting in lymphocutaneous sporotrichosis. This form of disease, called ascending lymphangitis, is characterized by nodules along draining lymphatics, and the appearance of lesions at sites distant to the initial infection.
A widely available, low-cost option for treating sporotrichosis is oral potassium iodide. This treatment option, however, can lead to thyroid imbalance or gastrointestinal symptoms, and has been a second-line to antifungal drug therapy.
Antifungal therapy with itraconazole is the recommended first-line treatment for cutaneous sporotrichosis. This is an azole drug that is often used, but patients can also be given other antifungals, such as terbinafine or fluconazole. Therapy is typically given for three to six months, and if disseminated disease occurs, amphotericin B should be used.
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