Sporotrichosis is a subcutaneous infection caused by the fungus Sporothrix schenckii and is acquired from moss, decaying vegetation, hay, and soil. It is usually seen in those whose vocation brings them into contact with the environment. The two primary manifestations involve the cutaneous and lymphocutaneous systems; however, osteoarticular, pulmonary, and disseminated forms (primarily in immunocompromised patients) may be seen from direct inoculation or through hematologic seeding.
The extremities are usually involved with the initial lesion at the site of injury from a thorn, barb, pine needle, or wire. After approximately 1 to 10 weeks, a localized red, purple, or pink papule develops, often resembling an insect bite. The papule evolves into one or more nodules that form painless chronic ulcers with a nonpurulent, clear discharge. In the lymphocutaneous form, the nodules will progress proximally along lymphatic tracts and blood vessels. Many strains do not grow at temperatures above 35°C, decreasing their ability to spread and commonly resulting in a localized lesion. It is not communicable from person to person, although it may be acquired through exposure to infected animals, with cats being the most infectious.
Wearing gloves and long sleeves while working in the outdoors and avoidance of skin contact with sphagnum moss are the mainstays of prevention. Confirmatory diagnosis is made with biopsy or culture.
Management and Disposition
Treatment with oral itraconazole for 3 to 6 months, or alternatively potassium iodide or terbinafine, is effective, with complete recovery in cutaneous and lymphocutaneous forms. Variable response to treatment, often initially with amphotericin B, is seen in patients with severe disease or systemic involvement.
This diagnosis should be considered when a cutaneous lesion is found on a patient involved with landscaping, rose gardening, Christmas tree farming, berry picking, or baling of hay, and in veterinarians.
Lesions typically are noted on the distal upper extremity, and the patient may have already failed multiple treatments with antibacterial agents.
While first described in the southern and central United States, it is most common in Mexico, Central/South America, Japan, Australia, and Africa. In Peru, the incidence is approximately 1 in 1000 people.
Sporotrichosis is easily confused with leishmaniasis, and the two illnesses coexist in many locations. Lymphatic spread is more characteristic of sporotrichosis, but possible with either. Other diseases or causes on the differential include Nocardia, tularemia, and mycobacteria.
Sporotrichosis. Typical sporotrichoid spread up the arm from an inoculation of the hand. Note the ulcers that resemble pyoderma gangrenosum in this Panamanian child. (Photo contributor: Richard P. Usatine, MD. Used with permission. From Usatine RP, Smith MA, Mayeaux EJ, Chumley HS. The Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw Hill; 2013: Fig. 174-13.)
Sporotrichosis. Typical lymphatic spread ...