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Aiding in the diagnosis of extracutaneous sporotrichosis
Sporotrichosis is an endemic fungal infection caused by the dimorphic fungus Sporothrix schenckii. Most cases of sporotrichosis have been reported from the subtropical and tropical regions of the Americas, but a global distribution is likely. The organism is often isolated from soil, plants, or plant products (wood), and occupational or recreational exposure to these materials is often implicated in infected individuals.
Infections due to S schenckii can be differentiated into several distinct syndromes:
-The cutaneous form of the disease is most common, often arising from sites of minor skin trauma. The primary erythematous, papulonodular lesion may range from several millimeters to 4 cm in size. Secondary lesions develop proximally along lymphatic channels. These generally painless lesions usually do not involve lymph nodes, although lymphadenopathy may develop.
-Extracutaneous sporotrichosis can be manifested as osteoarticular involvement of a single joint. Major joints of the extremities (ankle, knee, elbow, hand) are most often involved. The affected joint is swollen and painful, with an attendant effusion. Systemic symptoms are minimal.
-Pulmonary sporotrichosis with cavitary lesions also has been described.
-A multifocal extracutaneous syndrome has been described, consisting of multijoint involvement, or widely scattered cutaneous lesions. Constitutional symptoms (fever, weight loss) are often noted, and spread to bone and central nervous system may occur. Underlying immune system suppression is often a contributing factor. Untreated infection is ultimately fatal.(1)
Extracutaneous infections, including disseminated and articular infections, produce positive tests. The test should be positive in approximately 90% to 95% of all primary sporotrichosis infections. Specimens from these patients may become positive by 2 weeks after infection and are not expected to remain positive for more than 7 months after the original primary infection.
Agglutination titers of > or =1:8 indicate presumptive evidence of sporotrichosis. Titers of 1:4 to 1:8 are commonly seen in normal persons.
Some cutaneous infections are associated with negative serologic results.
A negative test does not exclude the possibility of sporothrix infection since the test is only positive in the early stages of infection.
The presence of high titers of rheumatoid factor in the patient specimen may cause false-positive reactions.
1. Rex JH, Okhuysen PC: Sporothrix schenckii. In Principles and Practice of Infectious Diseases. Edited by GL Mandell, RG Douglas, JE Bennet. Philadelphia, Churchill Livingstone, 2000, pp 2695-2699
2. Barros MB, de Almeida Paes R, Schubach AO: Sporothrix schenckii and Sporotrichosis. Clin Micro Rev 2011;24(4):633-654