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Fig. 6.45 A-E. Disseminated skeletal coccidioidomycosis. A A solitary lytic defect in a rib. B, C CT scans of a paraspinal abscess and vertebral lesions. D A lytic lesion in the inferior pubic ramus. E Lytic defects in the upper end of the left and the lower end of the right sacroiliac joint.

 

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Sporotrichosis

Although this is primarily a cutaneous fungus, it is important for radiologists because disseminated forms occur, involving not only the lungs but also the genitourinary tract, bones, joints, muscles and meninges. It is quite a common infection in parts of the world.

Synonyms

Schenck's disease. Beurmann-Gougerot's disease. Ger: de Beurmann Krankheit. Fr: Maladie de Beurmann-Gougerot. Sp: Esporotricosis.

Definition

Sporotrichosis is infection with the dimorphic fungus Sporothrix schenckii. There is a less common variety, S. schenckii var. luriei.

Geographic Distribution

Sporothrix schenckii is found worldwide, particularly in the soil. S. schenckii var. luriei was first described in 1969 and has been isolated in South Africa and Europe. There is a varying incidence of human infection. Sporotrichosis is quite common in Mexico and parts of Central and South America (El Salvador, Brazil, Uruguay, Venezuela, Colombia), particularly where there is high humidity and moderate temperature. It is found in Japan and elsewhere in Asia, and in Australia and southern Africa. It is uncommon in dry or cold regions.

Epidemiology and Pathology

Sporotrichosis usually results from traumatic inoculation, either while working with soil, or from thorns or splinters. Epidemics have occurred: for example, 3000 cases in the Witswatersrand, South Africa, where the timber used as pit props in the mines was heavily contaminated with S. schenckii. Gardeners, florists and others working with plants are at risk. In Uruguay, 80% of patients have been infected by the claws of armadillos: other animals and even human fingernails are another source of infection. Infection has occurred after handling a burrowing fish, presumably from contact with the soil and contamination of wounds. There is no gender or race predilection, but sporotrichosis is more frequent in children and young adults, probably as a result of increased exposure to soil and vegetation. Alcoholics are at particular risk for the pulmonary and disseminated forms. It is not contagious, but familial cases occur from exposure to a common source.

The systemic form probably results from inhalation. Histopathologically, as with other mycoses, there is a diffuse inflammatory pyogranulomatous reaction, with progression to fibrosis. The fungus may not be found easily in the involved tissue, and culture may be necessary to identify it. In the lung there may be hyperplasia of the mucosa, described as pseudocarcinomatous. In the disseminated disease there may be both yeast forms and hyphae. The histopathological findings (Fig. 6.48) vary with different strains of the fungus and the patient's immune status.

Progressive lesions in the lung develop as nodules, cavities, or diffuse infiltration. Both the lung tissue and regional lymph nodes may undergo caseating necrosis. Spontaneous remission may occur as a result of a strong immunological response.

The laboratory diagnosis depends on recognition of the fungus, either in scrapings form the edge of the lesions or by culture of exudates or biopsy specimens. Agglutination, immunoassay, and immunofluorescent tests are valuable, particularly in disseminated infections. There is a sporotrichin skin test which is very reliable, but because asymptomatic infections occur, a positive reaction does not always indicate active infection.

 

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