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An infectious disease caused by the plant saprophyte Sporothrix schenckii and characterized by the formation of nodules, ulcers, and abscesses, usually confined to the skin and superficial lymph channels but occasionally affecting the lung or other tissues (eg, synovial membranes).
Etiology, Incidence, and Pathology
S. schenckii is characteristically found on rosebushes, barberry bushes, sphagnum moss, and other mulches. Farm laborers, gardeners, and horticulturists, especially those handling barberry bushes or sphagnum moss, are most often infected. The pathologic picture is mainly suppurative.
Symptoms and Signs
The most common form, cutaneous-lymphatic, occurs characteristically on the hand and arm. The primary lesion, usually on the finger, begins as a small, movable, nontender, subcutaneous nodule that slowly enlarges, adheres to the skin, becomes pink and later necrotic, and finally ulcerates. In a few days or weeks, similar discolored subcutaneous nodules appear along the course of the lymphatics draining the area. Local pain, heat, and general symptoms (fever, chills, malaise, or anorexia) are notably absent.
Inhalation of the fungus may cause pneumonia, localized infiltrates, or cavities (sometimes bilateral). Symptoms are relatively mild, and the course is chronic.
Though S. schenckii has only rarely been cultured from the blood, it seems reasonable to explain other extracutaneous disease as hematogenous dissemination from either a subclinical cutaneous lesion or, perhaps more likely, a pulmonary focus. Bone, periosteum, or synovium is involved in 80% of such cases; muscle and eye, in others. Involvement of the spleen, liver, kidney, genitalia, or CNS is rare.
Diagnosis
Diagnosis is by culture and identification of S. schenckii. Unlike other pathogenic fungi, S. schenckii is rarely seen in fixed tissue, even with special stains.
Prognosis and Treatment
The cutaneous-lymphatic form is chronic, indolent, and rarely fatal. It responds readily to potassium iodide saturated solution, initially 1 mL orally tid, increased by 1 mL/day to an optimal dose of 3 to 4 mL tid. The solution may be diluted in water or other beverage and should be taken after meals. Therapy must be continued and may be well tolerated for prolonged periods. However, iodism may appear at any time as an irritative phenomenon of the skin and mucous membranes (eg, rashes, coryza, conjunctivitis, stomatitis, laryngitis, bronchitis). When symptoms develop, the dose should be decreased or the drug temporarily discontinued. After a 1- to 2-wk interruption, the drug may be cautiously resumed at a lower dosage. Iodide medication may need to be continued despite iodism; in such cases, iodide sensitivity may lessen or disappear despite continued therapy.
In disseminated disease, amphotericin B IV (see General Therapeutic Principles, above) may be helpful, since about 30% of patients have died, in some instances despite extensive treatment with iodides. Treatment with ketoconazole has yielded disappointing results; itraconazole is under evaluation.
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