JPC SYSTEMIC PATHOLOGY

INTEGUMENT SYSTEM

September 2016

I-M35

 

Signalment (JPC #3070330):  One-year-old neutered male Chihuahua

HISTORY:  Focal alopecia in the right scapular area at the site of a rabies vaccination that was given 12 weeks previously.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin and subcutis:  Disrupting and replacing over 80% of adipocytes within the panniculus adiposus there is an inflammatory infiltrate surrounded by abundant pale, “smudgy” collagen exhibiting diminished fiber detail and decreased birefringence (necrosis), admixed with fibrin, edema and necrotic debris.  The inflammatory infiltrate is composed of numerous macrophages with abundant microvacuolated cytoplasm, few neutrophils and numerous lymphocytes and plasma cells that often form dense perivascular nodular aggregates and obscure vessel walls.  Multifocally, there are moderate amounts of vaccine product, characterized by amphophilic granular material, both within macrophages and free in the extracellular matrix.  Within the overlying dermis, hair follicles and adnexa are small and superficial (atrophic) with fragmented hair shafts and are surrounded by similar pale, “smudgy” collagen.  The superficial dermis is multifocally infiltrated by low numbers of macrophages, lymphocytes, and neutrophils, and there is rare pigmentary incontinence.  There multifocal globular deposits of excess melanin pigment within hair shafts and epithelium of the external root sheaths.  The overlying epidermis is multifocally minimally hyperplastic and focally eroded with replacement by a serocellular crust composed of degenerate neutrophils, hemorrhage, serum and fibrin.  Previously described inflammatory cells multifocally infiltrate the panniculus carnosus and skeletal muscle fibers are occasionally degenerate or necrotic.

MORPHOLOGIC DIAGNOSIS:  Haired skin and subcutis:  Panniculitis, granulomatous, diffuse, marked, with follicular atrophy and loss, extracellular and intrahistiocytic vaccine material, and lymphoplasmacytic perivascular dermatitis, Chihuahua, canine.

CONDITION:  Post-rabies vaccination panniculitis

SYNONYMS:  Poodle patch

GENERAL DISCUSSION:

PATHOGENESIS:

CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

For gross findings:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Infectious nodular and diffuse granulomatous and pyogranulomatous diseases of the dermis. In: Skin Diseases of the Dog and Cat, Clinical and Histopathological Diagnosis. 2nd ed. Ames, IA: Blackwell; 2005: 538-542.
  2. Mauldin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. St. Louis, MO: Saunders Elsevier; 2016: 542, 612-614.
  3. Miller WH, Griffin CE, Campbell KL. Small Animal Dermatology. 7th ed., St. Louis, MO: Elsevier Mosby; 2013:483, 561-563. 


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