L5 - Endocrine and Immune Mediated Skin Dz PDF

VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II INTEGUMENTARY SYSTEM  Integumentary system Lectures Topics  L1-3 General introduction of the integumentary system Dermatohistopathology Primary and secondary skin lesions Disorders and diseases...

VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II INTEGUMENTARY SYSTEM  Integumentary system Lectures Topics  L1-3 General introduction of the integumentary system Dermatohistopathology Primary and secondary skin lesions Disorders and diseases of skin  L4 Endocrine and immune-mediated diseases of skin  L5 Viral, bacterial and mycotic diseases of skin  L6 Parasitic and neoplastic diseases Integumentary system: lecture 4 Contents  4.1 Endocrine diseases  4.2 Immune-mediated diseases  4.1 Endocrine diseases : Hypothyrodism  Due to inadequate production of thyroxine &  Alopecia (bilateral triidothyronine, eg: pituitary neoplasia, symmetrical) thyroidal atrophy, iodine deficiency  Remaining hair; coarse, dull, dry, brittle, easily epilated, fail to regrowth after clipping  Skin; dry, slightly scaly hyperpigmented, 20 seborrheia, and/or pyoderma  4.1 Endocrine diseases : Hypothyrodism  Common in dogs  Typical atrophic dermatosis pattern  Often hyperplasia of epidermis / follicular infundibulum  Increase in dermal mucin as seen in photo (alcian blue stain)  Histo: epidermal changes, orthro- and/or parakeratotic hyperkeratosis and many follicular "plugs" filled with keratin and cutaneous debris, collagen stained unevenly VPM 3417: VETERINARY PATHOLOGY III 4.1 Endocrine diseases : Hyperadrenocorticism  Due to excessive exposure of endo or exogenous glucocorticoids  Typical endocrine changes and often thin, poor healing skin.  Gross: macule, hyperpigmentation, alopecia (bilateral symmetrical), remaining hair: coarse, dull, brittle, dry, easily epilated, fail to regrowth after clipping, skin: hypotonic, easily bruising, poor wound healing, 2o seborrheia, and/or pyoderma  4.1 Endocrine diseases : Hyperadrenocorticism  Alopecia & comedones VPM 3417: VETERINARY PATHOLOGY III 4.15.1 Endocrine Endocrine diseases diseases : Hyperadrenocorticism  Calcinosis cutis - most common source is dystrophic calcification, which occurs in soft tissue as a response to injury  White to dark plaque-like areas on the skin of the ventral abdomen  4.15.1 Endocrine Endocrine diseases diseases : Hyperadrenocorticism  Calcinosis cutis: showing multifocal to coalescing aggregates of mineral scattered throughout the dermis  Mostly seen in iatrogenic Cushing’s disease  4.1 Endocrine diseases  Other: eg. Testosterone-responsive dermatosis, hyperestrogenism (rare)  Hormones act on skin & other organs by modifying existing physiological processes  Bilateral symmetrical alopecia (nonpruritic)  Hyperpigmentation  20 seborrheia and/or pyoderma 4.2 Immune-mediated diseases  Hypersensitivity (HS) or allergic dermatoses  Hypersensivity:  Type I (anaphylatic)  Type II (cytotoxic)  Type III (immune complex)  Type IV (cell mediated)  Eg. Allergic contact dermatitis, flea allergy dermatitis 4.2 Immune-mediated diseases Type 1 (anaphylatic) Type II (cytotoxic) 4.2 Immune-mediated diseases Type III (immune complex) Type IV (cell mediated) 4.2 Immune-mediated diseases  Hypersensitivity (HS) reactions  Definition  in response to normally harmless foreign compounds (Ag’s)  most cutaneous HS's are mediated by types I or IV HS reactions  pruritus is a common feature of most HS's 4.2 Immune-mediated diseases Atopic dermatitis  Common in dogs; less in cats and horses  Complex HS type I to normally non-toxic exogenous Ag's  Possible dysfunction of Th2 cells with overproduction of specific IgE  Mast cell degranulation-pruritus self-trauma  4.2 Immune-mediated diseases Allergic Contact Dermatitis [Contact HS]  Prolonged contact (sensitization) with the offending allergen (eg plants, cleaners, synthetic carpets plastic dishes, rubber chew toys, etc)  Early lesions of erythema, papules/ plaques and vesicles at contact areas (esp haired regions)  4.2 Immune-mediated diseases  Atopic dermatitis: pruritus self-trauma erythema, excoriation, alopecia (esp face / feet / abdomen), hyperpigmentation & lichenification 4.2 Immune-mediated diseases 4.2 Immune-mediated diseases Atopic dermatitis VPM 3417: VETERINARY PATHOLOGY III  4.2 Immune-mediated diseases  Dermatitis with  May see spongiosis &/or eosinophils & mast cells eosinophilic early and later microabscesses ("nibbles") mononuclear cells  4.2 Immune-mediated diseases  1.0  Alopecia and excoriations  Alopecia due to excessive “grooming” 4.2 Immune-mediated diseases Crusted papules of “miliary dermatitis” 4.2 Immune-mediated diseases Flea allergy dermatitis (Flea-bite hypersensitivity)  Most common hypersensitivity of cats and dogs, in flea endemic areas  Combination of types I & IV HS to antigens in flea saliva  Once sensitized, few fleas contribute for severe reaction  4.2 Immune-mediated diseases Flea allergy dermatitis (Flea-bite hypersensitivity)  Intense pruritus self trauma / secondary infections  Primary lesion is an erythematous papule or wheal  Self-trauma alopecia, excoriation & crusts  Chronicity hyperpigmentation & lichenification  Excoriation, crusts & early lichenification of lateral thorax & lumbosacral area 4.2 Immune-mediated diseases Some other hypersensitivity reactions  Food Hypersensitivity (Food Allergy)  Equine Insect (Culicoides) Hypersensitivity  Angioedema (edematous swellings) Urticaria (hives or wheals)  Induced by penicillin, food, or insect bite.  Signs: often pruritic swellings of dermis  Lesions; multiple, transient, flat-topped edematous papules or plaques (focal elevation of the hair coat)  Histo: epidermal spongiosis, dermal oedema, perivascular infiltrate of lymphocyte and eosinophil cells 4.2 Immune-mediated diseases Urticaria – microscopic features  4.2 Immune-mediated diseases  Autoimmune reactions: when autoAb’s or T cells react against self Ag’s. Most have hereditary predisposition; rare in domestic animals (dogs > horses, cats)  Pemphigus : autoAb’s attack desmogleins, loss of adhesion (called acantholysis). Cause blisters that slough off and form sores and intraepidermal pustules  Acantholysis = loss of adhesion between keratinocytes  4.2 Immune-mediated diseases  Pemphigus: - Vesicles, bullae, erosions, acantholysis - Dx: Demonstration of Ab either in the skin lesions or in serum (usually IgG, less common, IgM or IgA) - Eg: pemphigus foliaceous, pemphigus vulgaris, bullous pemphigoid, pemphigus vegetans  Lupus erythematosus: collection of autoimmune diseases - Discoid (localized to the skin) - Systemic (affect multiple tissues including the skin) Blistering diseases  4.2 Immune-mediated diseases Pemphigus foliaceous  Subcorneal pustule with numerous acantholytic cells mixed with neutrophils  Immune staining of deposits of intracellular autoimmune IgG in the upper epidermal region 4.2 Immune-mediated diseases Pemphigus foliaceous  Primary lesion is superficial pustules  Oftenly obscured by hair coat or have ruptured because they are fragile 4.2 Immune-mediated diseases Pemphigus foliaceous  Widespread alopecia, scaling and crusting  4.2 Immune-mediated diseases Pemphigus foliaceous  Thick crusts on footpads  Crusts result from adherence of the content of ruptured pustules to the skin surface  4.2 Immune-mediated diseases Pemphigus foliaceous  Numerous pustules and epidermal collarettes  4.2 Immune-mediated diseases Pemphigus vulgaris  4.2 Immune-mediated diseases Bullous pemphigoid  Chronic, inflammatory, subepidermal, blistering autoimmune disease  Subepidermal vesicles/pustules with complete separation of the intact epidermis (including basal layer) from the dermis VPM 3417: VETERINARY PATHOLOGY III  4.2 Immune-mediated diseases Bullous pemphigoid  Vesicles / bullae which often rupture to leave ulcers  Severe ulcerative dermatitis on the abdomen.  Punctate lesions coalesced to form large ulcerative lesions.  Note the similarity to erythema multiforme, cutaneous drug reactions, and vasculitis  4.2 Immune-mediated diseases Discoid (cutaneous) lupus erythematosus  UV light alters keratinocyte Ag’s autoimmune reaction interface dermatitis, pigmentary incontinence  Interface dermatitis, dense lichenoid band of lymphocytes & plasma cells  Apoptotic keratinocytes (left arrow)  Melanophage (right arrow) VPM 3417: VETERINARY PATHOLOGY III  4.2 Immune-mediated diseases Discoid (cutaneous) lupus erythematosus  Alopecia  Erythema  Erosion, ulceration, crusting & depigmentation of nasal planum region  4.2 Immune-mediated diseases Some other immune- mediated disorders  Immune-mediated Vasculitis  Erythema Multiforme  Toxic Epidermal Necrolysis  Plasma Cell Pododermatitis  Cutaneous Amyloidosis Infarction of facial skin following immune-mediated vasculitis Circulatory disturbances VPM 3417: VETERINARY PATHOLOGY III