ISSN 2398-2950      

Phaeohyphomycosis and Hyalohyphomycosis


Synonym(s): For both Hyalohyphomycosis and Phaeohyphomycosis: Mycetoma, Fungal granuloma, Opportunistic fungal infection, Saprophytic fungi, Soil fungi, Yeast infection. for Phaeohyphomycosis alone: Black fungi, Black mold, Black yeast, Chromomycosis, Dematiaceous fungi.


  • Cause: phaeohyphomycosis and hyalohyphomycosis are a diverse group of environmental mycotic infections caused by dematiaceous (dark colored) and non-pigmented (transparent or hyaline) saprophytic fungi whose morphologic characteristics in tissue can include filamentous hyphae and/or, yeast-like cells.  
  • Signs:
    • Skin: slow growing, firm to fluctuant, poorly circumscribed, possibly darkly pigmented, dermal and/or subcutaneous nodules +/- ulceration and draining tracts.   
    • CNS: clinical signs of fungal infection of the brain depend on the location of the infection; they include seizures, vertical nystagmus, anisocoria, cranial nerve deficits, altered mentation, ataxia, head tilt and paresis. 
  • Diagnosis: initial rapid cytology (modified Wright’s) followed by fungal culture, histopathology (hematoxylin eosin initially then special staining using periodic-acid Schiff (PAS), Grocott-Gomori methenamine silver and/or Fontana-Masson, FungiFluor). Species identification can be performed by PCR with partial ITS (internal transcribed spacer) sequencing. 
  • Treatment: combined surgical excision with concurrent, prolonged systemic antifungal treatment. 
  • Prognosis: good if single lesion which can be totally excised with a wide margin, but very poor if chronic, deep and/or disseminated infection. 



  • A saprophytic mycotic / mold infection caused by an array of filamentous fungi, ubiquitous soil and environmental saprophytes Sacrophytic fungi (Phaehyphomycosis / Hyalophomycosis).  
  • Pathogens causing phaeohyphomycosis (melanistic hyphae) in dogs and cats include species from Alternaria, Bipolaris, Cladophialophora and Curvularia genera. Genera with species causing disease in cats, but not in dogs, are Exophiala, Fonsecaea, Macrophomina, Microsphaerosis, Moniliella, Phialophora, Phoma, Scolecobasidium and Stemphylium.  
  • Genera with species causing hyalohyphomycosis (transparent hyphae) in cats (and other mammals) include Fusarium, Acremonium, Paecilomyces, Pseudallescheria, Sagemonella, Phialosimplex and Scedosporium.

Predisposing factors


  • Outdoor access, but exclusively indoor cats have been affected (environmental fungi / molds).  
  • (Contact with other cats or prey species.) 
  • Local infections are rarely associated with systemic diseases or immunosuppression. 
  • The infrequent cases of systemic disseminated infection may or may not be associated with immunosuppression, especially chronic or high dose corticosteroid treatment. However, the majority of case reports were in FeLV and FIV negative cats.   


  • Puncture wounds especially wood splinters. 
  • (Fight-bite wounds). 
  • (Water contamination of open wound (putative)). 
  • Inhalation.


  • Traumatic implantation (sharp wood injury > bite-fight) → soil/organic material(/water) contaminates tissue → opportunistic fungal infection starts → single or multiple nodules/plaques → ulceration + slow spread to adjacent tissues (including bone) → (colonization of respiratory tract?) → ± encephalitis or focal abscesses in central nervous system.


  • Long duration.


  • Extremely rare.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Rahimi T, Mohammadi R (2020) Identification of Dermatophyte and Nondermatophyte Molds Isolated from Animal Lesions Suspected to Dermatomycoses. Adv Biomed Res 9,4 PubMed
  • Daly JA, Hubka V, Kubátová A, Gimeno M, Barrs V R (2019) Feline disseminated cutaneous phaeohyphomycosis due to Exophiala spinifera. Med Mycol Case Rep 27, 32-35 PubMed.   
  • Velázquez-Jiménez Y, Hernández-Castro R, Romero-Romero L, Salas-Garrido C G, Martínez-Chavarría L C (2019) Feline Phaeohyphomycotic Cerebellitis Caused by Cladosporium cladosporioides-complex: Case Report and Review of Literature. J Comp Pathol 170, 78-85 PubMed
  • Brooks I J, Walton S A, Shmalberg J, Harris A (2018) Novel treatment using topical malachite green for nasal phaeohyphomycosis caused by a new Cladophialophora species in a cat. JFMS Open Rep 4(1), 2055116918771767 PubMed.  
  • Leao A C, Weiss V A, Vicente V A, Costa F, Bombassaro A, Raittz R T, Steffens M B, Pedrosa F O, Gomes R R, Baura V, Faoro H, Sfeir M Z, Balsanelli E, Moreno L F, Najafzadeh M J, de Hoog S, Souza E M (2017) Genome Sequence of Type Strain Fonsecaea multimorphosa CBS 980.96T, a Causal Agent of Feline Cerebral Phaeohyphomycosis. Genome Announc 5(7), e01666-16 PubMed.  
  • Russell E B, Gunew M N, Dennis M M, Halliday C L (2016) Cerebral pyogranulomatous encephalitis caused by Cladophialophora bantiana in a 15-week-old domestic shorthair kitten. JFMS Open Rep 2(2), 2055116916677935 PubMed
  • Overy D P, Martin C, Muckle A, Lund L, Wood J, Hanna P (2015) Cutaneous Phaeohyphomycosis Caused by Exophiala attenuata in a Domestic Cat. Mycopathologia 180(3-4), 281-287 PubMed.  Erratum in: Mycopathologia 180(3-4), 289.    
  • Seyedmousavi S, Netea M G, Mouton J W, Melchers W J G, Verweij P E, de Hoog G S (2014) Black yeasts and their filamentous relatives: principles of pathogenesis and host defense. Clin Microbiol Rev 27, 527-542 PubMed.  
  • Sugahara G, Kiuchi A, Usui R, Usui R, Mineshige T, Kamiie J, Shirota K (2014) Granulomatous pododermatitis in the digits caused by Fusarium proliferatum in a cat. J Vet Med Sci 76(3), 43543-43548 PubMed.    
  • Quimby J M, Hoffman S B, Duke J, Lappin M R (2010) Adverse neurologic events associated with voriconazole use in 3 cats. J Vet Intern Med 24(3), 647-649 PubMed.  
  • Miller R I (2010) Nodular granulomatous fungal skin diseases of cats in the United Kingdom: a retrospective review. Vet Dermatol 21(2), 130-135 PubMed
  • Dye C, Johnson E M, Gruffydd-Jones T J (2009) Alternaria species infection in nine domestic cats.  J Feline Med Surg 11, 332-336 PubMed.
  • Abramo F, Bastelli F, Nardoni S, Mancianti F (2002) Feline cutaneous phaeohyphomycosis due to Cladophyalophora bantiana. J Feline Med Surg 4(3), 157-163 PubMed.  
  • Halaby T, Boots H, Vermuelen A, Van Der Ven A, Beguin H, Van Hooff H, Jacobs J (2001) Phaeohyphomycosis caused by Alternaria infectoria in a Renal Transplant Recipient. J Clin Microbio 1952-1955 PubMed
  • McKay J S, Cox C L & Foster A P (2001) Cutaneous alternariosis in a cat. J Small Anim Pract 42 (2), 75-78 PubMed.
  • Dhein C R, Leathers C W, Padhye A A, Ajello L (1988) Phaeohyphomycosis caused by Alternaria alternata in a cat. J Am Vet Med Assoc 193(9), 1101-1103 PubMed.   

Other sources of information

  • Miller W H, Griffin C E, Campbell K L (2013) Muller and Kirk’s Small Animal Dermatology. 7th edition. St Louis, MO: Elsevier Mosby, pp 244-245.
  • Reviews:
    • Lloret A, Hartmann K, Pennisi M G, Ferrer L, Addie D, Belák S, Boucraut-Baralon C, Egberink H, Frymus T, Gruffydd-Jones T, Hosie M J, Lutz H, Marsilio F, Möstl K, Radford A D, Thiry E, Truyen U, Horzinek M C (2013) Rare systemic mycoses in cats: blastomycosis, histoplasmosis and coccidioidomycosis: ABCD guidelines on prevention and management. J Feline Med Surg 15(7), 624-637 PubMed
    • Lloret A, Hartmann K, Pennisi M G et al (2013) Rare opportunistic mycoses in cats: phaeohyphomycosis and hyalohyphomycosis: ABCD guidelines on prevention and management. J Feline Med Surg 15 (7), 628-630 PubMed.
    • Grooters A M & Foil C S (2006) Miscellaneous fungal infections. In: Greene CE (ed). Infectious diseases of the dog and the cat. 3rd ed. St Louis.Saunders Elsevier. pp 637.


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