Skin nontumor
Infectious disorders
Algal infection-Prototheca

Topic Completed: 1 July 2011

Minor changes: 17 August 2020

Copyright: 2002-2020,, Inc.

PubMed Search: Prototheca

Nat Pernick, M.D.
Page views in 2019: 494
Page views in 2020 to date: 401
Cite this page: Pernick N. Algal infection-Prototheca. website. Accessed October 21st, 2020.
Definition / general
  • Not fungi but similar features
  • First recognized as human pathogen in 1964; 2 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;172:207)
  • 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
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 #225)
  • Amphotericin B if disseminated, surgical excision if focal cutaneous or subcutaneous
Clinical images

Images hosted on other servers:

Lesion on foot

Microscopic (histologic) description
  • Necrotizing granulomas of subcutis containing spherical organisms with central basophilia, internal septation and double layer cell walls
  • Also multiple endospores 2 - 4 microns
Microscopic (histologic) images

Images hosted on other servers:

Various images

Internal septation

H&E, GMS and PAS


Positive stains
Additional references
Back to top
Image 01 Image 02