Sporotrichosis is a subacute or chronic fungal infection caused by dimorphic species belonging to the Sporothrix genus, collectively known as the Sporothrix schenckii complex. Among these, Sporothrix schenckii is the most common cause, while other species, such as Sporothrix brasiliensis, Sporothrix globosa, Sporothrix pallida, and Sporothrix mexicana, are less frequent causes of disease.

Sporotrichosis is found worldwide, with endemic areas in Latin America, especially Brazil, Mexico, and Colombia, and in Asia, mainly China, India, and Japan. Sporadic cases have been reported in the United States and Australia.

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 chronic obstructive pulmonary disease (COPD), 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, and 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.