Dermatology Flashcards
Skin Lesions can be classified into 7 categories based on how they actually appear, what are these categories?
- Changes in Skin Colour
- Rashes
- Lose of Haid
- Excessive Scaling
- Changes in Skin thickness
- Defects in skin integrity
- Lumps and Swelling
What are the two major skin colour changes seen in dogs?
- Erythema - skin that is redder than normal, implying that the skin is inflammed, usually due to allergic, parasitic, infectious and immune mediated causes
- Hyperpigmentation : Skin that is darker than normal leading to black coloured skin; usually due to a chronic change in allergic disease and Malassezia dermatitis and a hormanal effect in endocrine disorders.
- (Cats and Horses do not hyperpigment)
What is the skin colour change seen here?
Erythema
Explain the skin colour changes in this picture
Erythemic papula with some pustials
What does Econofication mean?
Swelling
What is happening here?
Hyperpigmentation
Explain what is happening here.
Loss of pigment, Erosion, Ulcer and Crust
Explain the difference between Erosion and Ulcer
- Erosion = loss of skin but does not bleed
- Ulcer - hits the basement membrane and bleeds
What is a Rash?
A rash is a collection of skin lesions usually comprised of erythematous papules, pustules (maculo-papulo-pustular eruption)
Explain what a Erythematous Macule is
- Macules - circular, flat area of erythematous skin upto 1cm in diameter
- Often seen with staphylococcal pyoderma, fleabite hypersensitivity and contact dermatitis
What is a papule?
Where are they most seen?
- small, red, raised, circular solid mass less than 1cm in diameter
- Papules are most commonly seen with staphylococcal pyoderma, fleabite hypersensitivitys, scabies, atpoic dermatitis, fly bite hypersensitivity and contact dermatitis
What is a Pustule?
What are pustles associated with?
- Pustules: red, circular sports containing central, yellow sac of pus.
- Pustules are usually associated with staphylococcal pyoderma
Explain what this is?
Staphylococcal Ring
- Central, circular area of alopecia (may or may not be hyoperpigmented) surrounded by a rim of erythema with a ring of peripheral scaling (an epidermal collarette)
Alopecia is a common presenting sign in both cats and dogs. It may occur spontaneously or be secondary to pruritus.
What is spontaneous alopecia a sign of?
Spontaneous alopecia is a sign of disorders affecting the hair follicle such as follicular infections and endocrine disorders.
What is this dog suffering from?
This dog has a symmetric diffuse alopecia of the hind limbs.
He is suffering from Folicular Distrophy
Explain Excess Scale and what happens in normal skin.
In normal skin the superficial layers of the stratum corneum (corneocytes) are being continuously desquamated into the environment. In some disease states, the process is disrupted leading to visible skin lesions.
What is Hyperkeratosis?
- is a pathological term meaning thickening of the stratum corneum.
- Clinically the term should be reserved for accumulations of thick adhearent keratin on the nasal planum of footpad.
What is a comedone?
- Dilated hair follicle filled with with cornified cells and sebaceous material appears black or brown.
- Diseases that affect hair follicles such as demodicosis, endocrine diseases and cornification defects.
What are follicular casts?
- Follicular cases: an adherent sheath of scale surrounding a hair shaft above the skin surface.
- This lesion results from follicular hyperkeratosis and is usually found in sebaceous adenitis and cornification defects.
Changes in skin thickness
Skin may become either thicker of thinner than normal.
Describe skin thickening and Thinning?
What are the two major changes seen in dogs?
- Increased skin thickness :- can be caused by thickening of the epidermis or dermis, or infiltration of the skin wiht inflammatory cells.
- Decreased skin thickness :- occurs due to a combined thinning of the epidermis and dermis
- The two major changes that are seen in dogs are Lichenification and Cutaneous atrophy
What is this skin change?
Lichenification
What is this skin change and why has it changed?
Cutaneous atrophy
Loss of Elastin
What is a Plaque
Plaque - a localised patch of thickened skin with a flat surface >1cm; most common example is a feline eosinophilic plaque
Describe the following Skin Integrity defects
- Erosion
- Ulcer
- Vesicle
- Draining Tracts/Sinus
- Erosion
- a shallow defect in which the epidermis is missing but the basement membrane is intact.
- Ulcer
- A deeper defect in which the epidermis is absent exposing the underlying dermis; commonly caused by autoimmune and immune mediated diseases, deep infections
- Vesicle
- A blister less than 1cm in diameter; form due to lack of cohesion between the epidermis and dermis; rare in animals.
- Draining Tract/Sinus;
- an opening between the underlying dermis or subcutis and the skin surface through which exudate is normally discharging. Sinuses are normally associated with deep infections.