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Background

This is an achlorophylic algaelike unicellular organism, related to the green algae Chlorella. These organisms are found in many settings including rivers, lakes, and sewage-laden areas. The cutaneous lesions are usually secondary to trauma with inoculation and implantation. These skin lesions may be non-specific in appearance with papules, nodules, or herpetiform lesions.

DISEASE ASSOCIATIONS CHARACTERIZATION
Immunocompromised states  

 

PATHOGENESIS CHARACTERIZATION
General

Unicellular endospores or multicellular sporangia

Endospores reproduce by internal septation and evolve into sporangia

Prototheca sporangia are referred to as morula-with a central endospore surrounded by 5 endospores

Two pathogenic species in humans:

Prototheca wickerhamii Most human cases of diseases
Prototheca zopfii Less common cause of disease

 

GROSS APPEARANCE/CLINICAL VARIANTS CHARACTERIZATION
General  
VARIANTS  
Superficial cutaneous

Papulonodular or ulcerative lesion or as drainage from a wound or surgical site

Progress slowly with mild tenderness and drainage

Olecranon bursitis Usually follows non-penentrating trauma
Systemic infection Br J Dermatol 1996;135:803-806

 

HISTOLOGICAL TYPES CHARACTERIZATION
General-SKIN

Granulomatous dermatitis in dermis and subcutaneous tissue
Organisms may be present freely or within the cytoplasm of multinucleated giant cells

Spherical with thick walls and often a have a clear halo around them

Internal septation and endospore formation is noted

VARIANTS  

 

SPECIAL STAINS/IMMUNOPEROXIDASE/OTHER CHARACTERIZATION
Special stains GMS or PAS stains in tissue sections

 

DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES
Coccidoides  

 

PROGNOSIS AND TREATMENT CHARACTERIZATION
Prognostic Factors Slowly progressive disease with low grade chronic inflammation
Treatment Surgical excision
Intravenous amphotericin B
Ketoconazole

Arch Pathol Lab Med 1987;111:737-740.
Principles and Practice of Infectious Disease. 5th Ed. New York, NY: Churchill Livingstone Inc;1990:2033.


Commonly Used Terms

Microbiology


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Last Updated 1/7/2001

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