38-11: Sporotrichosis

Sporotrichosis is a chronic fungal infection caused by organisms of the Sporothrix schenckii complex. It is worldwide in distribution; most patients have had contact with soil, sphagnum moss, or decaying wood. Infection takes place when the organism is inoculated into the skin—usually on the hand, arm, or foot, especially during gardening, or puncture from a rose thorn. In recent years, significant zoonotic transmission of Sporothrix brasiliensis has been documented in Brazil and Argentina driven by domesticated cat bites and scratches.

The most common form of sporotrichosis begins with a hard, nontender subcutaneous nodule. This later becomes adherent to the overlying skin and ulcerates. Within a few days to weeks, lymphocutaneous spread along the lymphatics draining this area occurs, which may result in ulceration. Cavitary pulmonary disease occurs in individuals with underlying chronic lung disease. Articular disease may simulate rheumatoid arthritis and delay diagnosis.

Disseminated sporotrichosis is rare in immunocompetent persons but may present with widespread cutaneous, lung, bone, joint, and CNS involvement in immunocompromised patients, especially those with cellular immunodeficiencies, including AIDS and alcohol use disorder.

Cultures are needed to establish diagnosis. The usefulness of serologic tests is limited, but they may be helpful in diagnosing disseminated disease, especially meningitis.

Itraconazole, 200–400 mg orally daily for several months, is the treatment of choice for localized disease and some milder cases of disseminated disease (Table 38–1). Terbinafine, 500 mg orally twice daily, also has good efficacy in lymphocutaneous disease. Amphotericin B intravenously, 0.7–1.0 mg/kg/day, or a lipid amphotericin B preparation, 3–5 mg/kg/day, is used for severe systemic infection. Surgery may be indicated for complicated pulmonary cavitary disease, and joint involvement may require arthrodesis.

The prognosis is good for lymphocutaneous sporotrichosis; pulmonary, joint, and disseminated disease respond less favorably.