Week 1 SYSTEMIC.pdf
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Portal of Entry into the Skin 1 Factors cause injury of the skin 1. External factors:Exogenous factors 2. Internal factors: Endogenous factors 2 ❖ Gross morphology of skin lesions 1. Primary lesions:...
Portal of Entry into the Skin 1 Factors cause injury of the skin 1. External factors:Exogenous factors 2. Internal factors: Endogenous factors 2 ❖ Gross morphology of skin lesions 1. Primary lesions: are arise from the same organ ✓ are the direct result of the underlying disease process ✓ most important diagnostically 2. Secondary lesions : they are coming from somewhere else ✓ evolve from primary lesions (via self-trauma, altered keratinization, etc) ✓ less important diagnostically Primary Lesions Macule: area of altered skin color (discoloration), up to 1 cm lentigo = a benign heritable condition of hyperpigmentation; due to focal increase in number of melanocytes Papule: a small ( 1 cm) round solid elevation of the skin Plaque: a larger, flat-topped solid elevation in the skin Papules and plaques on the trunk of a dog that developed a contact allergy to a shampoo. ©Paul Hanna Nodule: hard solid elevation of skin, 1 cm, that usually extends into the deeper layers Vesicle: well circumscribed, < 1 cm diameter, elevation of the epidermis, or below the dermal-epidermis filled with clear fluid Bulla: a large vesicle (blister) > 1 cm diameter, localized collection of fluid within epidermis Tumor: a large mass (neoplasia implied) that may involve any structure of the skin or subcutis Cyst: an epithelial lined cavity containing fluid or solid material Pustule: a small, circumscribed, pus filled elevation of the epidermis Abscess : small circumscribed accumulation of pus within epidermis or within follicle Wheal: a smooth, sharply circumscribed elevation of skin, due to dermal edema Wheals are most commonly seen with hypersensitivity (allergic) disorders in horses (above) and less frequently with dogs (left). Lesions that can be Primary or Secondary Scale - an accumulation of (flakes / dandruff) on the surface of skin Crust : accumulation of dried exudate, blood / serum, Idiopathic photosensitization Comedo : a dilated hair follicle filled with cornified cells and sebaceous material (1 or 2) Comedones seen in dog with hyperadrenocorticism (Cushings) Abnormalities of hair Alopecia - loss of hair Hypotrichosis less hair than normal atrichia (absence) – failure to develop Effluvium / defluxion – excessive shedding Hypertrichosis (hirsutism) : more hair than normal Hirsutism due to pituitary adenoma of the pars intermedia in a horse Alteration in epidermal pigmentation consist of: 1. Hyperpigmentation: an increased production of melanin from existing melanocytes 2. Hypopigmentation: can be congenital Is due to lack of melanocytes, failure of melanocytes to produce melanin 3. Pigmentation Incontinence: Loss of melanin pigment from the basal layer of the epidermis. Factors can affect melanin pigment production Melanocyte-stimulating hormone Age Inflammation Temperature genes 16 Hyperpigmentation Red (erythema) - inflammation / vasodilation Black - hypermelanosis (melanoderma) / melanotrichia 17 Hypopigmentation Leukoderma is due to decreased pigmentation of skin 18 Secondary Lesions Epidermal collarette: a circular rim of Ulcer: a break in the epidermis with exposure of keratin flakes following loss of the "roof" of the underlying dermis vesicle or pustule Excoriation: erosions or ulcers Scar: an area of fibrous tissue that has replaced caused by scratching, biting, or the damaged dermis and /or subcutis rubbing. Excoriation in a dog with sarcoptic mange Fissure: a linear cleavage of usually Lichenification: a thickening and thickened, inelastic skin hardening of the skin with exaggeration of the superficial markings Lichenification and alopecia in a bovine with sarcoptic mange
