Skin inflammatory (nontumor)
Infectious disorders
Fungi - North American blastomycosis

Author: Nat Pernick, M.D. (see Authors page)

Revised: 18 October 2018, last major update July 2011

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Fungi - North American blastomycosis [title]

Cite this page: Pernick, N. Fungi - North American blastomycosis. website. Accessed October 20th, 2018.
Definition / general
  • Skin lesions usually secondary to pulmonary blastomycosis when soil containing mycelia is disturbed and airborne conidia are inhaled (Clin Microbiol Rev 2010;23:367); pulmonary disease may be subclinical
  • Rarely occurs at site of penetrating injuries
  • Due to Blastomyces dermatitidis, a spherical, double-contoured, 12 micron yeast that reproduces by budding
  • Endemic areas are Mississippi, Missouri and Ohio river valleys (USA) and southern Canada
  • Risk factors are immunosuppression, collagen vascular disease, being an outdoor worker, having a coworker with blastomycosis (Can J Infect Dis Med Microbiol 2009;20:117)
  • May affect healthy patients via spore inhalation; usually men > women because they participate more in activities that disturb infected soil
Clinical features
  • Slowly enlarging verrucous plaques containing multiple small abscesses
Case reports
  • Itraconazole or long term amphotericin
Clinical images

Images hosted on other servers:

Various images

Microscopic (histologic) description
  • Marked pseudoepitheliomatous hyperplasia of epidermis
  • Granulomatous and neutrophilic infiltrate
  • Fungi are within giant cells
  • Blastomyces dermatitidis is a 12 micron, spherical, double-contoured yeast with broad based buds
Microscopic (histologic) images

Images hosted on other servers:

Pseudoepitheliomatous hyperplasia, epidermal abscesses and prominent dermal infiltrate
High power shows fungal organisms

Budding yeast

Figure 1A: gross; 1B: atypical squamous proliferation infiltrating into deep dermis; 1C: intraepithelial neutrophilic abscesses; giant cell with round, broad based budding yeast

Giant cell with round, broad based budding yeast

Differential diagnosis
  • Alternaria species: may have similar histologic features, but differentiate based on culture (J Cutan Pathol 2011;38:923)
  • Squamous cell carcinoma: may resemble pseudoepitheliomatous hyperplasia of fungal infection, but has marked atypia and invasion
Additional references