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Semester II Pathology > Skin Pathology 1 > Flashcards

Skin Pathology 1 Flashcards

-Outline structure and function of the skin and the importance of dermatology in veterinary medicine. -Explain the concept of patterns of skin disease in relation to epidemiology, clinical presentation, histopathology. -Give examples of how breed, sex, geographical location, and time of year may influence the incidence and prevalence of skin disease. -Explain, with examples, how macroscopic pathology of skin lesions may provide a clue to pathogenesis or aetiology. -Explain, with examples

1
Q

WHY STUDY THE SKIN?

A

Largest organ in the body.
Provides crucial defence from environment.
Skin problems VERY common in small animal practice (1 in 5 consultations).
Skin disease is a major cause of morbidity and economic loss in farm animals worldwide.
Animal disease provides insights and models for human disease.

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2
Q

STRUCTURE OF THE SKIN

A

Epidermis- basal, spinous, granular, cornified layers (deep to superficial), basal cells.
Basal layer contains dendritic Langerhans cells, melanocytes,
Dermis- cells, fibres, matrix (ground substance), vascular supply and innervation- sensitive.
Apoliposebaceous complexes- hair follicles and associated sweat (apocrine) and sebaceous glands.
Hypodermis (subcutis, panniculus)- fat and fibrous tissue.

Compound hair follicles seen in carnivores.

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3
Q

FUNCTION OF THE SKIN

A

-Physical protective barrier
-Immunity- skin immune system
-Thermoregulation
-Blood pressure regulation
-Sensory perception
-Secretions (communication)
-Storage (fat etc)
-Vitamin D production (especially herbivores)
The skin barrier is self repairing.

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4
Q

PATTERNS OF SKIN DISEASE

A
  1. EPIDEMIOLOGY- breed, sex, location, season.
  2. CLINICAL PRESENTATION- lesions, distribution, configuration.
  3. HISTOPATHOLOGY- pattern analysis.
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5
Q

PATTERNS OF SKIN DISEASE- EPIDEMIOLOGY

A

eg. BREED- skin fold dermatitis (intertrigo) in Sharpei, Bulldog, Pekingese.
SEX- symmetrical alopecia- particular distribution due to oestrogen production in by Sertoli cell tumours in male dogs (especially cryptorchids)
LOCATION- cutaneous hemangiosarcoma due to sun exposure in dogs in West Indies, Grenada.
SEASON- flea allergy dermatitis- more common in temperate climates, seen year round. Seen truly seasonally in colder climates. Lesions often due to self trauma from itchiness.

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6
Q

PATTERNS OF SKIN DISEASE- CLINICAL PRESENTATION

A 
Clinical signs relate to macroscopic pathology. 
Lesion DISTRIBUTION (location), DESCRIPTION (size, shape, colour, consistency, location), lesion TYPE eg. inflammatory, hyperplastic, alopecic, hypertrichotic, tumoural/neoplastic (nodular- not all nodules are neoplastic!)
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7
Q

LESION DISTRIBUTION DIAGRAMS

A

Used to illustrate distribution of lesions.
Some skin diseases have characteristic lesion patterns.
eg. Ventral lesions, edges of ear- sarcoptic mange.
eg. More irregular, dorsal lesions, muzzle/front paws of puppies- demodectic mange.

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8
Q

PRIMARY SKIN LESIONS

A

Develop spontaneously as a result of underlying disease.
Useful in trying to determine pathogenesis and aetiology of disease.
Biopsying EARLY will help to determine primary skin lesions.
-MACULE or PATCH (patch if >1cm)
-PAPULE or PLAQUE (if >1cm)
-VESICLE or BULLA (>1cm)
-PUSTULE or ABSCESS (more complicated than pustule)
-WHEAL or ANGIOEDEMA (massive oedema)
-CYST
-NODULE (1-2cm) or TUMOUR (>2cm)

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9
Q

MACULE

A

A circumscribed, NON PALPABLE spot characterised by a change in the colour of the skin.
No change in consistency of skin.
A macule larger than 1cm is called a PATCH.

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10
Q

PAPULE

A

A small, solid ELEVATION of skin, less than 1cm diameter. Palpable- usually reflects accumulation of cells/fluid in an inflammatory reaction.
Macules and papules commonly present together- maculopapular reaction.

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11
Q

PLAQUE

A

A large (>1cm) FLAT TOPPED elevation, formed by extension or coalescence of papules.

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12
Q

NODULE

A

A circumscribed, solid elevation, less than 1cm diameter.

Usually caused by massive cell infiltration, that may be inflammatory or neoplastic.

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13
Q

TUMOUR

A

A mass of more than 2cm that, strictly speaking, may be neoplastic or non-neoplastic (eg. granulomatous), though the term is often used to imply neoplasm.

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14
Q

PUSTULE

A

May be intraepidermal, subepidermal, or follicular. Typically contain neutrophils and bacteria, but may contain eosinophils and/or be sterile.
Tend to be transient in animals- may only see a ‘popped’ pustule.

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15
Q

ABSCESS

A

A deep, localised accumulation of pus in an are of tissue destruction, surrounded by inflammation.
Usually more deeply located than a pustule.

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16
Q

VESICLE or BULLA

A

Sharply circumscribed epidermal elevation filled with clear fluid. May be intraepidermal or subepidermal.
Bulla- similar to a vesicle, but larger than 1cm diameter.
Fragile lesions.

17
Q

WHEAL (HIVE)

A

A circumscribed, raised lesion due to oedema, often transient. Localised.
ANGIOEDEMA- more severe/deep/extensive oedema. Can reach the dermis/subdermis.

18
Q

CYST

A

An EPITHELIUM LINED cavity, containing fluid or solid (inspissated) material. Smooth, well circumscribed, usually fluctuant (move when pressed).

19
Q

DIFFERENTIAL DIAGNOSIS OF MASS LESIONS

A
  1. Abscess
  2. Granuloma
  3. Cyst (simple? Parasitic?)
  4. Neoplasm
  5. Haematoma- a collection of blood cells can present as a mass lesion.
20
Q

SECONDARY SKIN LESIONS

A 
Evolve from primary lesions or are induced by self trauma or external factors. 
Secondary lesions complicate the clinical picture and make diagnosis difficult. 
-EPIDERMAL COLLARETTE
-EXCORIATION
-EROSION or ULCER
-FISSURE
-SCAR
-LICHENIFICATION
-CALLUS
21
Q

COLLARETTE

A

A circular rim of scale (loose or peeling keratin) that evolves from a pustule, vesicle or bulla.
More commonly seen than the primary lesions that lead to them- pustules, vesicles and bullae are fragile, transient lesions.
If a collarette is found, look for an intact pustule to allow biopsy.

22
Q

EXCORIATION

A

Erosions or ulcers caused by SELF TRAUMA ie. scratching, rubbing or biting. Typically linear in conformation, they generally indicate PRURITIS.
Can sometimes be an indication of pain.

23
Q

EROSION

A

A shallow epidermal defect that does not penetrate the basement membrane and thus heals by regeneration, without scarring.

24
Q

ULCER

A

An epidermal defect that reaches deep enough to expose the underlying dermis. Results from a deep pathological process and heals by deposition of fibrous connective tissue and scar formation.

25
Q

FISSURE

A

A linear cleavage of epidermis, may also include dermis, due to disease or injury, that appears as a sharply defined cleft or multiple small cracks.
Particularly seen in footpads- dried, dessicated skin.

26
Q

SCAR

A

Connective tissue repair of dermal injury results in fibrous tissue that replaces normal skin components.
Connective tissue is deposited parallel to skin surface to maintain skin tension.

27
Q

LICHENIFICATION

A

Thickening and hardening of the skin produces exaggerated skin markings (wrinkles etc.). Typically due to friction; areas may be hyperpigmented due to reaction of melanocytes.

28
Q

CALLUS

A

A localised area of rough, thickened, hyperkeratotic skin forming an alopecic, often lichenified plaque. Due to long term friction eg. elbow patches in outdoor dogs.

29
Q

LESIONS THAT MAY BE PRIMARY OR SECONDARY

A
  • ALOPECIA
  • SCALE
  • CRUST
  • FOLLICULAR CASTS
  • COMEDONES
  • PIGMENT ALTERATION
30
Q

SCALE

A

An accumulation of keratinised cells. Normal loss of keratinised cells is not visible to the naked eye; scale is abnormal.
May be thick, thin, dry or oily- depends on the animal, location and underlying cause.

31
Q

CRUST

A

Formed from dried exudate (serum, blood, cells, scales) that adheres to the skin surface.
Commonly blood and serum- exudative dermatitis.

32
Q

COMEDONES

A

Singular- COMEDO.
A plug of cornified cells and sebaceous material within the dilated lumen of a hair follicle.
Follicular casts are ‘microcomedones’

33
Q

FOLLICULAR CASTS

A

An accumulation of keratinous debris that adheres to the hair shaft and protrudes from the follicle ostium on to the skin surface.

34
Q

PATTERNS OF SKIN DISEASE- HISTOPATHOLOGY

A

Pattern analysis. Skin biopsy interpretation depends on:

  • Location and distribution of lesions (eg. lesions around blood vessels are commonly seen, as cells have entered the skin via haematogenous spread).
  • Type of change and cells involved.
  • Likely pathogenesis of the observed changes- what has happened to cause these changes?
35
Q

TYPE OF DISEASE

A

MINIMAL, MILD or SEVERE.
Consider epidemiology, clinical presentation, histopathology.
Chronicity? HOW LONG HAVE THE CHANGES BEEN GOING ON- the condition may have become secondary by the time the owner notices.

Semester II Pathology (24 decks)

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