Protothecosis

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

Internet Links

Microscopic Photo

Last Updated 1/7/2001

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

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