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Infectious disorders


Reviewer: Nat Pernick, M.D., PathologyOutlines.com, Inc. (see Reviewers page)
Revised: 4 December 2011, last major update July 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● Not fungi but similar features
● First recognized as human pathogen in 1964; two species associated with human disease - P. wickerhamii and P. zopfii
● Aerobic, achlorophyllous, algae-like, unicellular organisms in water, sewage and soil
● <100 cases of human infection reported, usually via trauma or contaminated water, involving face or exposed extremities with erythematous plaques, nodules or superficial ulcers
● Rarely infects toenails of patients with diabetes (Mycopathologia 2011 Apr 22 [Epub ahead of print])
● Primary cell or spherule is called the theca; species reproduce by internal septation, forming sporangia which contain up to 20 endospores
● P. wickerhamii: cells are rounder than the oval/cylindrical shapes of P. zopfii
● Diagnosis: corn meal agar


● Amphotericin B if disseminated, surgical excision if focal cutaneous or subcutaneous

Case reports

● 34 year old woman with index finger pain and hobbies of scuba diving and maintaining an aquarium (Arch Pathol Lab Med 2001;125:450)
● 73 year old man with nodules on leg secondary to splinter injury while chopping firewood (Case of Week #225)

Clinical images

Lesion on foot

Micro description

● Necrotizing granulomas of subcutis containing spherical organisms with central basophilia, internal septation and double layer cell walls
● Also multiple endospores 2-4 microns

Micro images

Various images

Internal septation

H&E, GMS and PAS


Positive stains

● GMS, PAS, mucicarmine (Arch Pathol Lab Med 2011;135:941)

End of Skin-nontumor / Clinical Dermatology > Infectious disorders > Prototheca

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