GPR: 2021 - Week 16

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Clinical history

52 year old male s/p renal transplant on immunosuppressive therapy presents with an indurated lesion on his left arm cultures were taken and the growth on potato dextrose agar is shown below. Which of the following choices is the most likely pathogen.


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Alternaria spp.
  • Dematiaceous fungi with over 50 different species
  • Alternaria alternata is the most common isolate in humans
  • Opportunistic pathogen especially in immunocompromised hosts
  • Fast growing olive to dark drown colonies
  • Dark brown color acquired via melanin in cell wall
  • suede to floccose texture



Aspergillus niger

  • Characteristic early yellow to white color which later turns black
  • reverse is a creamy white
  • filamentous fungi that tend to form hyphae
  • uniquely form dark brown/black pigment in conidial heads
  • Can be found in mycetoma and otomycosis



Scedosporium boydii

  • Aka Pseudallescheria boydii
  • another dematiaceous fungi
  • Greyish-white colony with grey-dark grey reverse
  • fast growing
  • can be associated with CNS infection
  • while growing in humans the fungi often lack pigment

Julian Villalba

John Branda


This week's Gross Pathology Roundup was presented by Leif Timothy Helland on MD.