Derm Dx: Ulcer on the index finger with painless red bumps on the forearm

Sporotrichosis is a fungal infection most often localized to the skin and soft tissues usually after traumatic inoculation with the dimorphic fungus, Sporothrix schenckii. Asymptomatic nontender skin lesions typically develop one to 12 weeks after initial inoculation and usually ulcerate...

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Sporotrichosis is a fungal infection most often localized to the skin and soft tissues usually after traumatic inoculation with the dimorphic fungus, Sporothrix schenckii.

Asymptomatic nontender skin lesions typically develop one to 12 weeks after initial inoculation and usually ulcerate followed by proximal nodular lesions that develop across lymphatic channels.

S. schenckii is found throughout the world in decaying vegetation, soil, wood, moss, thorns and hay. The fungus is endemic in certain areas of the U.S. including the Oklahoma, Missouri and Mississippi river valleys, as well as in regions of India, Japan and South America.

Most infections are non-life-threatening and occur following minor skin trauma in people with hobbies or occupations that involve gardening, landscaping or farming. Zoonotic transmission via cat scratches or bites from insects, armadillos, rodents and dogs is also possible.

Skin lesions occur predominantly in exposed areas of the upper extremities and face.

Extracutaneous sporotrichosis, including osteoarticular, pulmonary, meningeal and lymphangeal forms of the disease occur in about 5% of patients, usually in those with underlying chronic conditions such as alcoholism, diabetes, chronic obstructive pulmonary disease, AIDS and hematologic malignancies. Pulmonary and disseminated forms of infection can occur when S. Schenckii conidia are inhaled.

Diagnosis

Culture of biopsied skin lesions and histopathologic stains are necessary to distinguish sporotrichosis from other skin lesions with a proximal nodular lymphangitic spread, including cutaneous nocardiosis, cutaneous nontuberculous mycobacterial infections and cutaneous leishmaniasis.

Fungal cultures should be stored, as S. schenckii growth usually occurs within eight days but can take as long as four weeks.

Treatment

Antifungal therapy is necessary as spontaneous resolution is rare, with typical treatment ranging from three to six months. Clinical improvement is usually observed within four weeks.

For fixed cutaneous or lymphocutaneous sporotrichosis, first line treatment is with itraconazole with data from several open treatment trials indicating a 90% to 100% response rate.

For nonresponsive patients, clinicians can try higher doses of the itraconazole, but should monitor serum drug levels to insure adequate absorption of >1 microgram/mL.

Other options include saturated potassium iodide solution, which may be inconvenient to administer and not well tolerated.

High-dose terbinafine or fluconazole use has been reported with response rates ranging from approximately 60% to 80%. However, about one-third of patients treated with high-dose terbinafine experience adverse gastrointestinal and neurologic events. Clinicians should monitor liver function in patients taking terbinafine.

Patients with AIDS or other immunocompromised conditions, and those with meningeal or disseminated sporotrichosis, should receive secondary suppressive itraconazole therapy to prevent clinical relapses.

References:

1. Hay RJ. Sporotrichosis. In Freedberg IM, Isin AZ, Wolff K, et al. Fitzpatrick’s Dermatology in General Medicine. 5^th ed. New York: McGraw-Hill; 1999: 2372-2373.

2. Kauffman CA. Sporotrichosis. Clin Infect Dis. 1999;29:231-236.

3. Kauffman CA, Bustamante B, Chapman SW, et al. Clinical practice guidelines for the management of sporotrichosis: 2007 update by the Infectious Diseases Society of America. Clin Infect Dis. 2007;45:1255-1265.