Sporotrichosis is caused by the dimorphic fungus Sporothrix schenckii, found worldwide, but more commonly in tropical and subtropical climates. The organism resides in decaying vegetation, plants, and soil. Cutaneous infection usually results from traumatic inoculation. Sporotrichosis is the most common and least severe of the deep mycoses.

The lesions of sporotrichosis may present in 3 different patterns.

• Lymphocutaneous or sporotrichoid pattern – 75% of cases
• Fixed cutaneous – no lymphatic dissemination; may be more likely to develop in patients previously sensitized to S schenckii
• Disseminated cutaneous – occurs with systemic involvement; rare and usually in the context of immunosuppression such as oral prednisone therapy, other immunosuppressive medications, alcohol use disorder, diabetes mellitus, hematologic malignancies, and AIDS

Extracutaneous disease is rare but manifests with osteoarticular involvement in immunocompetent individuals, whereas immunocompromised patients typically present with multisystem involvement. Pulmonary sporotrichosis is associated with alcohol use disorder, tuberculosis, diabetes mellitus, sarcoidosis, and steroid use.

Thorny plants, such as barberry and rose bushes, are the most common source of cutaneous inoculation of sporotrichosis. Other plant exposures include sphagnum moss, straw, hay, soil, and mine timbers. Occupational exposures include farmers, florists, gardeners, and forestry workers. Zoonotic transmission from scratch injury or bites of infected cats, rodents, or armadillos has been reported but is a less common mode of transmission.

Untreated cutaneous sporotrichosis usually waxes and wanes over months to years without systemic manifestations.