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Background
This fungal infection is caused by direct inoculation into the skin. The fungus is a normal component of soil and is also found on plants. Once inoculated, the fungus spreads through lymphatics and ascends to the proximal draining lymph nodes. Along the way, a series of linear nodules occurs. This pattern of spread is sometimes referred to as sporotrichoid spread. In disseminated disease, constitutional symptoms and arthralgias may occur.
OUTLINE
PATHOGENESIS CHARACTERIZATION Sporothrix schenkii Dimorphic fungus
Lives in soilDimorphic and develops a yeast form at 37C
At 25C, it forms sympodial conidiophores having 1-celled hyaline conidia on denticles that frequently occur as rosettes at the apices of swollen condiophores, and dematiaceous 1-celled conidia along the hyphae. The latter conidia arre typically present only in fresh isolated strains.
Rapid growing, moist, wrinkled, leathery to velvety in texture, at first white, becoming cream to dark brown or black at 25C
Conidiophores typically are present and are hypha-like, hyaline, septate, sympodial, and often have an inflated apex
Conidia are of two kinds:
1-celled, globose to clavate, arise solitarily on slender denticles, often forming rosettes
1-celled, thick-walled, dematiaceous, and arise along the hyphae
GROSS APPEARANCE/CLINICAL VARIANTS CHARACTERIZATION General VARIANTS Immunocompromised patients
HISTOLOGICAL TYPES CHARACTERIZATION General The pattern of inflammation is characteristically well circumscribed and granulomatous with central areas of acute suppuration
Demonstration of the organism in tissue is very difficult because the fungi are not numerous
The fungus is yeast like, subglobose to ovoid, 3-5 µm, in diameter with multiple blastocondia
The yeasts are not encapsulated
Asteroid body Globose to ovoid, basophilic cells, 3-5 µm in diameter with radiating eosinophilic rays up to 10 µm in diameter
Asteroid body formation appears to be more common in secondary lesions than in primary ones.
VARIANTS
SPECIAL STAINS/
IMMUNO-
PEROXIDASECHARACTERIZATION Special stains PAS and GMS stains positive Immunoperoxidase J Am Acad Dermatol 2001;44:261-4
Thirteen specimens of suspected sporotrichosis were selected for staining with anti-BCG antibody
Sporotrichoid infection was confirmed by histochemical staining, biopsy, and follow-up results
Results: Twelve of the 13 specimens stained positively using anti-BCG antibody
Of the 5 cultures done, 2 were positive for M marinum, and 1 grew Sporothrix schenckii.
Conclusion: Immunohistochemical staining with anti-BCG antibody offers another screening method to identify organisms in sporotrichoid infections because of its ease, cost-effectiveness, and simplicity
PROGNOSIS AND TREATMENT CHARACTERIZATION TREATMENT Oral potassium iodide continued for at least 4 weeks following clinical cure
Amphotericin B is used to treat relapsed lymphocutaneous disease
Antibacterial antibiotics are useful when secondary bacterial infections occur.
d-1hydroxystilbamidine and 5-fluorocytosine J Am Acad Dermatol 1999;40:350-355.
Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Twentieth Edition. WB Saunders. 2001.
Rosai J. Ackerman's Surgical Pathology. Ninth Edition. Mosby 2004.
Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Seventh Edition. WB Saunders 2005.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 5th Edition. McGraw-Hill. 1999.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.
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Last Updated April 4, 2005
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