Sporotrichosis
Section snippets
History
Sporotrichosis was first described by Benjamin Schenk at Johns Hopkins Hospital in 1898, but it was not until 1900 that Hektoen and Perkins named the etiologic fungi Sporothrix schenckii. Potassium iodide was first used as therapy by De Beurmann and Ramond in 1903, and in 1907 Lutz and Splendore characterized the asteroid body. The intradermal reaction produced by polysaccharides from the fungal mycelial phase was first used for diagnosis and epidemiological studies in 1947 by González-Ochoa
Epidemiology
Sporotrichosis is the most prevalent subcutaneous mycosis caused by species of the Sporothrix schenckii complex. It has a worldwide distribution, although it is more frequent in tropical and subtropical areas with warm (15-25°C) and humid (90%) climates. In South America, the estimated annual incidence is 48 to 60 cases per 100,000 population.3 Isolated cases are usually seen, although familiar and occupational epidemics have been reported.
In 1988, an epidemic occurred in the United States
Etiology
S schenckii complex comprises more than 6 species of closely related dimorphic fungi that can be found in soil or decaying matter. Animals, such as cats, dogs, horses, camels, donkeys, or rats, can act as vectors for the disease.9 Posttraumatic inoculation of the fungus is the usual form of entry; however, it can also be acquired by inhalation of spores, although this form of transmission is rare.10 In endemic areas, people exposed to low inoculums may develop immunity and have a positive
Pathophysiology
Once in the target organ, the fungus induces a granulomatous suppurative reaction in the host's tissues. Specific characteristics in different strains may confer variable virulence and a different response to treatment.16 T-cell immunity is important in limiting the disease.17 The presence of ergosterol peroxide, cell-wall compounds, and exoantigens have been described as virulence factors linked to activation of Th1 or Th2 responses.18 In the early phase of the disease, the Th1 response is
Classification
Sporotrichosis is classified as a primary cutaneous disease, with 3 different clinical presentations: lymphocutaneous, fixed, and disseminated. Extracutaneous disease includes osteoarticular, which is the most common,26 pulmonary, mucosal, or systemic.
In Mexico, lymphangitic sporotrichosis is observed in 60% to 80% of cases, fixed cutaneous in 10% to 30%, and systemic in 1% to 2%.1 In Japan, fixed cases can reach 60%. The other forms are rare.8 In children, the fixed cutaneous form is more
Clinical Presentation
The incubation period varies from days to months. In children, the most common site for cutaneous lesions is the face,27 whereas in adults the disease mainly affects the hands and arms.
Fixed sporotrichosis is characterized by a painless, infiltrated, erythematous, or violaceous plaque that may become verrucous or ulcerated (Figure 1). In the setting of chronic, nonhealing ulcers, sporotrichosis should be ruled out.29, 30
The lymphangitic form is characterized by an erythematous nodule that
Diagnosis
Clinical suspicion is essential for diagnosis. A detailed history regarding travel, occupation, or hobbies is important.40 Direct examination of exudate, sputum, or synovial fluid is not useful, because fungal structures are not usually observed. In approximately 50% of cases, the yeasts can be visualized with periodic acid-Schiff (PAS) or Gomori-Grocott (GG) stains on tissue smears. Fluorescence or immunohistochemical techniques almost always render positive identification of the fungus.
The
Differential Diagnosis
Sporotrichosis must be differentiated from tuberculosis, leishmaniasis, tularemia, cutaneous nocardiosis, other mycobacterial diseases, mycetoma, chromoblastomycosis, and leprosy.
Treatment
Sporotrichosis generally follows a benign course with a good response to treatment.8 Spontaneous healing can occur in many cases, including in pregnancy,46 although paradoxically, in this condition, dissemination has also been reported.
Potassium iodide is still considered first-line treatment in many third-world countries due to its low cost, efficacy, and safety profile47; however, there is no scientific evidence for or against its use.48 Its mechanism of action remains unknown, but it is
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