L4 - Disorder - Dz Of Skin PDF

Integumentary system: Lecture 1 Contents ❑ General Functions VETERINARY PATHOLOGY II ❑ SYSTEMIC VPM 3419: ❑ Normal structure INTEGUMENTARY ❑ Dermatohistopathology SYSTEM - Epidermal changes - Dermal changes - Subcutaneous cha...

Integumentary system: Lecture 1 Contents ❑ General Functions VETERINARY PATHOLOGY II ❑ SYSTEMIC VPM 3419: ❑ Normal structure INTEGUMENTARY ❑ Dermatohistopathology SYSTEM - Epidermal changes - Dermal changes - Subcutaneous changes VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Integumentary system: Lecture 3 DISORDERS AND DISEASES OF SKIN Contents ❑ 1. Congenital and hereditary ❑ 2. Disorders of keratinization ❑ 3. Disorders of pigmentation ❑ 4. Inflammation ❑ 5. Physiochemical diseases ❑ 6. Actinic diseases ❑ 7. Nutritional diseases VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 1. Congenital and hereditary ❑ Congenital: lesions develop in fetus (in utero) and are present at birth (eg. Hypotrichosis in fetus). ❑ Hereditary: inherited conditions transmitted genetically and not always manifested phenotypically in utero or at birth (Familial canine dermatomyositis). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Congenital and hereditary ❑ Epitheliogenesis imperfecta: discontinuities of the stratified squamous epithelium of skin, adnexa and/or oral mucosa (eg. calves & piglets). ❑ Possible inherited genetic mutation, pathogenesis not known ❑ Easily traumatised or infected – septicaemia; dehydration, electrolyte abnormalities New born calf with only 5-10% of skin on its body. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Congenital and hereditary ❑ Ichthyosis: inherited cutaneous disease. Marked hyperkeratosis & crack into plates causing cutaneous lesions resembling fish scales (eg. cattle & dogs). ❑ Defect due to failure of normal desquamation from increased adherence of keratinocytes. eg. Ichthyosis fetalis; skin is covered by large, horny plates separated by deep fissures, absence of hair. Histo: marked hyperkeratotic hyperkeratosis and lichenification. FATAL: fissuring → exudation of protein → bacterial & fungal infection VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 1. Congenital and hereditary ❑ Calf with ichthyosis - a congenital keratinization disorder. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Congenital and hereditary ❑ Others: eg. Hypotrichosis congenita (partial or complete absences of hair) due to maternal dietary iodine deficiency. Congenital hypotrichosis in an Ayrshire calf (note: thin hair coat due to failure of normal development of many of the hair follicles). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Congenital and hereditary ❑ Familial canine dermatomyositis: inherited inflammatory disease of skin and muscle; symmetrical scarring, alopecia of the face and limbs and atrophy of the muscles of mastication. Lesions develop as early as 7 weeks of age. ❑ Common in Shetland Sheepdogs, Collies. Other breeds include Chow Chow and Corgi. Autosomal dominant mode of inheritance with variable expressivity. ❑ The aetiopathogenesis of the condition is unknown; immunological damage occurs to blood vessels resulting in ischaemic damage to the skin and muscles. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 1. Congenital and hereditary ❑ Familial Canine Dermatomyositis – symmetrical alopecia on face. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Disorders of keratinization ❑ Seborrheic skin disease Chronic disease complex secondary to abnormalities of cornification and/or function of sebaceous glands with change from non-pathogenic resident bacteria to pathogenic, coagulase-positive Staphylococci. C/S : ranging from simple dandruff to severe inflammation with scaling and crusting. Aetiology: o Primary idiopathic seborrhea (MOST COMMON). o Secondary seborrhea mostly due to chronic inflammation or disorders such as hormonal imbalance (hypothyroidism, hyperadrenocorticism), ectoparasites (demodicosis), hypersensitivities (food allergy), sebaceous adenitis. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Disorders of keratinization ❑ Seborrheic skin disease Stages: keratinization with or without glandular function; scaling and crusting - surface lipids increase % of FFA and cholesterol and decrease % diester waxes - increase no. of surface bacteria. Histo: superficial perivascular dermatitis, marked epidermal hyperplasia, ortho- and parakeratotic hyperkeratosis, spongiosis, leukocytic exocytosis; lymphocytes, macrophages, mast cells and neutrophils (intraepidermal pustular dermatitis, folliculitis may be seen). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Disorders of keratinization ❑ Seborrheic skin disease Seborrhea sicca (dry) – dry skin with white to gray scales that exfoliate. Seborrhea oleosa (greasy) – Seborrheic dermatitis. brown or yellow pigment/lipids Seborrhea oleosa (greasy) adhered to hair & skin. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  3. Disorders of pigmentation ❑ Canine acanthosis nigricans: idiopathic dermatitis: hyperpigmentation, alopecia and lichenification. Seborrhea and bacteria pyoderma are frequent complications. Primary hereditary condition in Dachshund. Histo: thickened epidermis from acanthosis, hyperkeratosis, increased melanin pigment. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  3. Disorders of pigmentation ❑ Albinism: hypomelanosis, melanocytes are normally distributed, but are defective in function; inability to synthesize tyrosinase or failure of melanosome melanization in the presence of the enzymes. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  4. Inflammation ❑ Dermatitis: a non specific cutaneous inflammatory response with concomitant changes in the epidermis and dermis. ❑ Acute dermatitis: vesicles, pustules, erythema, oedema and exudation. Histo: spongiotic vesicles, spongiosis, intracellular oedema, vascular dilatation, and perivascular inflammatory cells. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  4. Inflammation ❑ Subacute dermatitis: erythema, edema and exudation, with or without crusts & mild to moderate vesiculation. Histo: similar to acute, but in addition, epidermal hyperplasia, ortho- and/or parakeratotic hyperkeratosis. ❑ Chronic dermatitis: mild erythema, scaling, crusts, lichenification and pigmentary disturbances. Histo: variable epidermal hyperplasia, ortho- and or parakeratosis hyperkeratosis, dermal oedema, vascular dilatation, and perivascular inflammatory cells. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  5. Physiochemical diseases ❑ Physical injury: physical stress include friction, pressure, vibration, electricity, high and low ambient temperature, humidity, visible, ultravoilets & infrared light & ionizing radiation. Cold injury: normally lesions developed not from the direct freezing and disruption of the cells, but from diminished blood flow to the point where tissue anoxia develops. Gross: include alopecia, scaling, and pigmentary alterations; severe cases - ischaemic necrosis, dry gangrene and sloughing. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  5. Physiochemical diseases Thermal injury: dry heat causes desiccation and carbonization, whilst moist heat causes boiling or coagulation. ❖Burns: ✓10 - only epidermis affected. ✓20 - epithelial cells coagulated, nuclei shrunken or karyorrhexic, marked vascular changes with marked dermal edema and spongiosis. ✓30- coagulation necrosis of both the epidermis and dermis; connective tissues, blood vessels and adnexa. Necrotic tissue sloughs & defect is filled in by granulation tissue. ✓40 - as those of 30 but penetrate below the dermis and beyond the subcutaneous fascia. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  5. Physiochemical diseases ❑ Physical injury: burn victim – note epidermal necrosis, ulcers / crusts. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  5. Physiochemical diseases ❑ Physical injury: acral lick dermatitis, note focal area of alopecia, erythema, erosion / ulceration. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  5. Physiochemical diseases ❑ Chemical injury: penetration of skin is enhanced by physical damage to the stratum corneum. Acids (eg. sulfuric acid), alkalines, turpentine. o Gross; marked erythema, swelling, a transient papular-vesicular stage that leads to ulceration and in severe cases, sloughing off the affected skin. Sequelae include, alopecia, scarring and alteration of skin and hair pigmentation. o Histo: superficial perivascular dermatitis either spongiotic or hyperplastic. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 5. Physiochemical diseases ❑ Chemical injury: primary contact irritant dermatitis. Contact irritant dermatitis (eg Contact irritant dermatitis (eg concentrated pour-on insecticide). concentrated lye solution). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  5. Physiochemical diseases ❑ Gangrenous necrosis of distal limbs due to ergotism. - Ingestion of grains/seeds infected by Claviceps purpurea producing ergotamine → endothelial damage → ischaemia → necrosis of distal extremities. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases ❑ Radiation of the sun (actinic radiation) are potentially harmful & can cause 10 phototoxicity "sunburn" & photosensitization. Phototoxicity: result from the direct damaging effect of radiation, usually shortwave ultravoilet, on unprotected skin (poor hair coats, damage stratum corneum and poor melanin pigmentation) which result injury to the cell nuclei, membranes, and organelles, inactivation of enzymes, mutagenesis and occasionally carcinogenesis eg. squamous cell carcinoma at the ears of cats with white ears. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 6. Actinic diseases ❑ Sunlight has 3 main regions of wavelength: i. Ultra Violet (UV) – 200-400 nm. ii. Visible – 400-700 nm. iii. Infrared >700 nm. ❑ UV rays divided into 3 types: i. UV A – 320-400 nm. ii. UV B – 280-320 nm (most damaging). iii. UV C – 200-280 nm (blocked by ozone). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 6. Actinic diseases ❑ Path of sunlight through atmosphere. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 6. Actinic diseases VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases ❑ Note, arrows indicate apoptotic keratinocytes (“sunburn cells”) due to UV-B radiation. These can be induced within 30 minutes of sun exposure. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases ❑ Feline solar dermatosis. Alopecia, erythema, erosions, and crusting on the ear pinna. As the disease progresses, papules will develop, with erosion and ulceration that suggest progression to squamous cell carcinoma. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases Photosensitization: most significant, it requires a photodynamic agent in the skin, which reacts with radiation of the appropriate wave length to induce tissue damage. Lesions: erythema, oedema, blisters, exudation, necrosis (skin dry and sloughs off); intense pruritic. ✓ Type I: ingestion or preformed photodynamic substances (from plants: buckwheat, St. John’s wort) or the photodynamic agents are exogenous eg. administration of anthelminitic (phenothiazine), antibiotics (tetracyclines, sulfonamides). ✓ Type II: endogenous pigment synthesis eg. Abnormal porphyrin metabolism – pigment accumulation. ✓ Type III: hepatogenous photosensitization, failure of the liver to eliminate phylloerythrin, a degradation product of chlorophyll. ✓ Type IV: idiopathic. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 6. Actinic diseases ❑ Photosensitization after treatment with a phenothiazine anthelmintic VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases ❑ Many plants contain chemicals which are photoreactive, eg St John’s wort. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 6. Actinic diseases ❑ Photosensitization associated with liver disease; note only poorly haired &/or white haired areas affected. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases ❑ Photosensitization in cattle; note only white areas affected. There is enough pigment in the colored hair to absorb / block the light and prevent activating the photodynamic agents. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  6. Actinic diseases ❑ Photosensitization in cattle; note only white areas affected. There is enough pigment in the coloured hair to absorb / block the light and prevent activating the photodynamic agents. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  7. Nutritional diseases ❑ Nutritional deficiencies: Hypovitaminosis: eg. Vitamin A deficiency; causes squamous epithelial cells to become hyperkeratotic and secretory epithelia to undergo squamous metaplasia. Mineral deficiency: eg. zinc: causes including decrease wound healing and keratinization defects in epidermis, hair, wool, and horny appendages. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Circulatory disturbances VPM 3417: VETERINARY PATHOLOGY III