JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

August 2016

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:  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 hyphae with nonparallel walls, and poorly discernible, irregularly angled, non-dichotamous 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.  Separating nodules of inflammation there are numerous reactive fibroblasts and loose fibrous connective tissue with perpendicularly arranged small caliber blood vessels (granulation tissue), progressing to more mature fibrosis.  Focally the wall of a large blood vessel is discontinuous with loss of endothelial cells and replacement by eosinophilic cellular and karyorrhectic debris and few previously described inflammatory cells (necrotizing vasculitis), and 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, rarely septate, with irregularly angled, non-dichotamous 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, hemorrhage, fibrin thrombi, necrotizing vasculitis, 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:

 


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