JPC SYSTEMIC PATHOLOGY
INTEGUMENTARY SYSTEM
August 2019
I-F02

Signalment (JPC# 21474-7,-8):  1-year-old, breed not specified, dog

HISTORY:  This dog from Texas had a severe, ulcerative dermatitis involving the legs.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin and subcutis:  Multifocally obscuring the dermis, separating and surrounding collagen fibers and adnexal structures, infiltrating the subcutis, and extending to all borders are coalescing, disorganized nodules composed of a core of cellular debris, fibrin, and drop-out (lytic necrosis) centered on faint, negative images of 6-10µm diameter hyphae with nonparallel walls and poorly discernible, irregularly angled, non-dichotomous branching.  Hyphae are surrounded by numerous degenerate and fewer viable neutrophils, epithelioid macrophages, fewer multinucleated giant cells (foreign body and Langhans’ types), and low numbers of eosinophils, plasma cells, and lymphocytes.  Inflammatory nodules are admixed with abundant hemorrhage, fibrin, hemosiderin-laden macrophages that often exhibit erythrophagocytosis, and colonies of 1-2um basophilic cocci.  Nodules of inflammation are separated by numerous reactive fibroblasts and loose, fibrous connective tissue with perpendicularly arranged small caliber blood vessels (granulation tissue), that progresses to more mature fibrosis.  The wall of a large blood vessel is focally discontinuous with loss of endothelial cells and replacement by eosinophilic cellular and karyorrhectic debris and few previously described inflammatory cells (vascular necrosis), and the lumen is partially occluded by a large fibrin thrombus.  Small vessels are often lined by reactive endothelial cells and are variably occluded by moderate amounts of fine to coarse fibrin with enmeshed erythrocytes and few inflammatory cells (fibrin thrombi). 

Gridley’s stain:  Hyphae are 6-10µm (occasionally up to 15µm) wide, thick walled, and rarely septate, with irregularly angled, non-dichotomous branching and thick, unevenly stained, non-parallel walls.

MORPHOLOGIC DIAGNOSIS:  Haired skin and subcutis:  Dermatitis and panniculitis, pyogranulomatous and eosinophilic, multifocal to coalescing, severe, with hyphae, vascular necrosis, hemorrhage, fibrin thrombi, and fibrosis, breed not specified, canine.

ETIOLOGIC DIAGNOSIS:  Cutaneous pythiosis

CAUSE:  Pythium insidiosum

CONDITION:  Oomycosis (formerly phycomycosis)

GENERAL DISCUSSION: 

PATHOGENESIS: 

TYPICAL CLINICAL FINDINGS: 

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

ULTRASTRUCTURAL FINDINGS: 

ADDITIONAL DIAGNOSTIC TESTS: 

DIFFERENTIAL DIAGNOSIS: 

COMPARATIVE PATHOLOGY: 

REFERENCES:

  1. do Carmo PM, Portela RA, Silva TR, et al. Cutaneous pythiosis in a goat. J Comp Pathol. 2015;152(2-3):103-5.
  2. Gaastra W, Lipman, LJ, De Cock AW, et. al. Pythium insidiosum: An Overview. Vet Microbiol. 2010; 146: 1-16.
  3. Grooters AM, Foil CS: Miscellaneous fungal diseases. In: Greene CE ed. Infectious Diseases of the Dog and Cat. 4th ed. St. Louis, MO: Saunders Elsevier; 2012: 677-681.
  4. Gross TL, Ihrke PJ, Walder EJ, et. al. Infectious nodular and diffuse granulomatous and pyogranulomatous diseases of the dermis. In: Skin Diseases of the Dog and Cat. 2nd ed. Oxford, UK: Blackwell Science; 2005: 303-309.
  5. Hargis AM, Myers S. The Integument. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:1083-1084.
  6. Heck LC, Bianchi MV, Pereira PR, et al. Gastric pythiosis in a bactrian camel. J Zoo Wildl Med. 2018; 49(3): 784-787.
  7. Maia LA, Olinda RG, Araújo TF, Firmino PR, et al Cutaneous pythiosis in a donkey (Equus asinus) in Brazil. J Vet Diagn Invest. 2016; 28(4): 436-9.
  8. Mauldin EA, Peters-Kennedy, J. Integumentary system. In: Maxie MG. ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: 657-659.
  9. Miller WH, Griffin CE, Campbell KL. Fungal and algal skin diseases. In: Muller & Kirk’s Small Animal Dermatology. 7th ed. Philadelphia, PA: Saunders Co; 2012: 257-259.
  10. Souto EP, Maia LA, Olinda RG, et al. Pythiosis in the nasal cavity of horses. J Comp Pathol. 2016; 155(2-3): 126-129.


Click the slide to view.



Click on image for diagnostic series.



Back | Home | Contact Us | Links | Help |