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.
What is a 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.
What is a nodule
A raised, firm, palpable mass >1cm
What is a cyst?
An epilthelial lined cavity filled with skin components such as corneocytes, keratin, hair or sebum
How does the dog manifest pruritus?
Marked variation in both the thresholds of different dogs and in their behaviour.
Dogs react differently with some dogs :-
- Chewing
- Scratching
- Biting
- Licking
- head-shaking
- Rolling on their backs
- Rubbing against furniture
How does the cat manufest pruritus?
Cats tend to overgroom which includes licking and rubbing.
Scratching is less common in cats but cats that do scratch tend to induce severe excoriations
What are the common causes of Pruritus in Dogs?
95% of cases are :-
- Ectoparasites
- Infections (Malassezia/Bacterial)
- Allergies
The remainder are Neoplasia and Immune Mediated (Pemphigus)
Alopecia in the dog is common
- Causes of alopecia can be differentiated into two broad categories, what are they?
- Excessive Hair Loss (mostly inflammatory causes) or
- Inadequate production of hair (non-inflammatory causes)
What are the most common causes of traumatic alopecia?
- Allergies
- Pruritic pyoderma
- Malassezia dermatitis
How do you tell if the hair loss is traumatic or Normal?
The hair is broken off in traumatic, normal it is pointy.
- How do you determine is the alopecia is inflamatory or non inflammatory?
- What does the typical inflammatory causes of alopecia incude?
- Inflammatory
- Look for the presence of inflammation and/or any primary lesions, such as papules or pustules, scale and crust
- Typical inflammatory causes of alopecia include bacterail folliculitis, dermatophytosis and demodicosis
What test do you use to see if the alopecia is:-
- Ringworm
- Demodex
- UV light
- Skin Scraping
- If the alopecia is non-inflammatory what pattern of heair loss would you see?
- What is the cause of the Alopecua in these cases?
- Diffuse, mostly bilaterally symmetric, alopecia that is usually confined to the trunk.
- The cause is inadequate production of new hair because of either abnormalities in morphogenesis (production of a new follicular shaft) or in Follicular cycling (signalling for the productin of a new shaft.)
What are the four phases of Hair Growth/Cycle?
- Anagen: Active Growth Phase
- Catagen: Transient Phase
- Telogen: Resting Phase
- Exogen: Old telogen shaft is shed and a new anagen hair replaces it.
What is the longest phase in most animals?
What animals is this not true?
- Telogen
- Breeds that require clipping eg Poodles, Sheep, Horse Manes and human scalp hair.
What are the 2 non-inflammatory reasons alopecia develops?
- Abnormality in the formation of the hair shaft (Dysplasia)
- Failure of the follicle to continuously cycle (Hair Cycle abnormality)
Follicular dysplasias have what common criteria?
- A strong predilection
- An onset in young to adult dogs
- A symmetrical regional alopecia often associated with hyperpigmentation
- Typical dermatohistopathologic abnormalities
- Absence of effective therapy, with only palliative measures
Why does Alopecia associated with hair cycle abnormalities occur?
THe hairs remain in telogen and fail to re-enter anagen
As no new hair growth is occuring the hair is gradually lost as a result of frictional forces, leading to the characteristic but often non-specific conical appearance.
Many disease are associated with hair cycle abnormalities including endocrine dermatoses (hypothyroisism, hyperadrenocorticism) Alopecia X, pattern alopecua of various breeds, cyclic flank alopecia, post clipping alopecia and anagen/telogen defluxion
- If a tumor is Malignant and of Epithelial origin what would it be called?
- Malignat and Mesenchymal?
- Carcinoma
- Adenocarcinoma (if its glandular)
- Sarcoma
Papllimavirus can lead to all of the following except :-
- Viral Pigmented plaques
- Bowenoid in situ carcinoma
- Fibrosarcoma
- Squamous Cell Carcinoma
- Sarcoids
C
Which of the following is a benign non-neoplastic lesion?
- Fibroadnexal hamartoma
- Haemangioma
- Meibomian gland adenoma
- Sarcoid
- Trichoblastoma
A
Which of the following neoplasms is nto dervied from the hair follicle?
- Trichoblastoma
- Pilomatricoma
- Meibomian Gland Adenoma
- Ceruminous Gland Carcinoma
- Infubdibular Keratinizing Acanthoma
D & E
Canine mast cell tumours are graded based on?
- Mitotic Index
- Previous History of Mast Cell tumour neoplasms
- Pleomorphism
- Inflitrative Pattern
- Immunohistochemical profile (EG. Ki-67, c-KIT)
A
What is a common clinicopathologic finding in patients diagnoses with anal sac gland adenocarcinoma?
- Hypokalemia
- Lymphocytosis
- Hyperglobulinaemia
- Anaemia
- Hypercalcaemia
E
