September 2016


Signalment (JPC # 21474-17):  Dog, breed unspecified

HISTORY:  This dog presented with pruritus and alopecia that was most severe in the skin of the lower back and base of tail.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin (2 sections):  Multifocally, primarily within the mid-dermis but extending into the panniculus, surrounding adnexa and occasionally vessels, minimally infiltrating follicular epithelium and separating adipocytes and collagen fibers are moderate numbers of neutrophils, macrophages, lymphocytes, plasma cells, and eosinophils.  Multiple hair follicles and apocrine glands are mildly ectatic.  Hair follicles contain keratin and cellular debris and, occasionally, low numbers of degenerate neutrophils and scattered 1 to 2 um diameter cocci (luminal folliculitis). Diffusely, there is epidermal hyperplasia characterized by acanthosis, spongiosis and prominent rete ridges, with orthokeratotic hyperkeratosis.  There is focal epidermal erosion with few eosinophils and neutrophils admixed with cellular debris (necrosis), hemorrhage, fibrin and edema in the underlying dermis. Diffusely, the superficial dermis is mildly expanded by clear space, dilated lymphatics (edema) and vascular congestion.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Dermatitis, periadnexal and perivascular, subacute, eosinophilic and lymphoplasmacytic, multifocal, moderate, with focal erosion, epidermal hyperplasia, and folliculitis, breed unspecified, canine.

ETIOLOGIC DIAGNOSIS:  Allergic dermatitis








Types of allergic skin diseases:



  1. Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Diseases of the dermis. In: Skin Diseases of the Dog and Cat, Clinical and Histopathological Diagnosis. 2nd ed. Ames, IA: Blackwell; 2005: 200-211.
  2. Kim HJ, Cronin M, Ahrens K, Papastavros V, Santoro D, Marsella R. A comparative study of epidermal tight junction proteins in a dog model of atopic dermatitis. Vet Dermatol. 2016;27(1): 40-e11.
  3. Kumar V, Abbas AK, Fausto N, Aster JC. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2015:200-211.
  4. Santoro D, Marsella R, Ahrens K, Graves TK, Bunick D. Altered mRNA and protein expression of filaggrin in the skin of a canine animal model for atopic dermatitis. Vet Dermatol. 2013; 24(3):329-336.
  5. 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: 590-598.
  6. Mineshige T, Kamiie J, Sugahara G, Yasuno K, et al. Expression of periostin in normal, atopic, and nonatopic chronically inflamed canine skin.  Vet Pathol. 2015;52(6):1118-1126.
  7. Nuttall T, Uri M, Halliwell R. Canine atopic dermatitis – what have we learned? Vet Rec. 2013;172(8):201-7.



Prototype Disorder

Immune Mechanisms

Pathologic Lesions

Body_ID: T006002.50




Immediate (type I) hypersensitivity

Anaphylaxis; allergies; bronchial asthma (atopic forms)

Production of IgE antibody → immediate release of vasoactive amines and other mediators from mast cells; recruitment of inflammatory cells

Vascular dilation, edema, smooth muscle contraction, mucus production, tissue injury, inflammation

Body_ID: T006002.100




Antibody-mediated (type II) hypersensitivity

Autoimmune hemolytic anemia; Goodpasture syndrome

Production of IgG, IgM → binds to antigen on target cell or tissue → phagocytosis or lysis of target cell by activated complement or Fc receptors; recruitment of leukocytes

Phagocytosis and lysis of cells; inflammation; in some diseases, functional derangements without cell or tissue injury

Body_ID: T006002.150




Immune complex- mediated (type III) hypersensitivity

Systemic lupus erythematosus; some forms of glomerulonephritis; serum sickness; Arthus reaction

Deposition of antigen-antibody complexes → complement activation → recruitment of leukocytes by complement products and Fc receptors → release of enzymes and other toxic molecules

Inflammation, necrotizing vasculitis (fibrinoid necrosis)

Body_ID: T006002.200




Cell-mediated (type IV) hypersensitivity

Contact dermatitis; multiple sclerosis; type I, diabetes; rheumatoid arthritis; inflammatory bowel disease; tuberculosis

Activated T lymphocytes → (i) release of cytokines → inflammation and macrophage activation; (ii) T cell-mediated cytotoxicity

Perivascular cellular infiltrates; edema; cell destruction; granuloma formation





Table 6-1 of Robbins and Cotran, 9th ed., 2014, Chapter 6, pg 201

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Click on image for diagnostic series.

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