Lesions Flashcards
Define primary skin lesion
Develops as a direct result of disease processes
Define secondary skin lesions
Develop as a consequence of patient’s activities
Compare secondary lesions and secondary pyoderma
- Lesion: due to patient’s actions
- Pyoderma: bacterial infection which is complicating and underlying skin disease e.g. allergy and demodicosis. Presents with primary lesions e.g. papules and pustules
What may linear lesions indicate?
External trauma or lesions associated with blood vessel, dermatome or congenital malformation
What may annular lesions indicat?
Peripheral spreading of disease (e.g. pyoderma or dermatophytosis)
What do symmetrical lesions indicate?
Systemically mediated disease (often endocrine)
Describe macules
- Primary lesion
- Circumscribed flat area of change in colour less than 1cm diameter
- Pigment loss or excess, erythema, haemorrhage
When are erythematous macules often seen?
Inflammatory disease of superficial dermis e.g. allergies
What is a patch?
Same as a macule but larger than 1cm diameter
What are petechiae?
Pinpoint macules caused by haemorrhage
What are ecchymoses?
Patches caused by haemorrhage of more than cm diameter
What are cutaneous haemorrhages often indicative of?
- Thrombocytopaenia
- Defects in coagulation
- Vasculitis
Describe papules
- Primary lesion
- Small solid elevation of skin less than 1cm diameter
- Local accumulation of inflammatory cells
- Flea allergy dermatitis, canine pyoderma
Describe plaques
- Primary lesions
- Large elevation of skin, sometimes formed by papules coalescing
- e.g. eosinophilic plaque in some cats with allergic skin disease
Describe nodules
- Primary lesions
- Solid elevation of skin greater than 1cm diameter
- Usually extends into deeper skin layers
What may nodules result from?
- Neoplasia (skin cells, or metastatic)
- Inflammatory cell accumulation (chronic granulomatous inflammation associateed with infectious or sterile processes)
- Less commonly, tissue dysplasia or hyperplasia with mineral deposition
What tests are useful in nodular diseases?
0 Needle aspiration and cytology
- Excisional biopsy and histopathology
- Excisional biopsy and culture
Describe cysts
- Primary lesion
- Cavity with an epithelial lining
Describe tumours
- Primary lesion
- Large mass involving skin structure
- Often relates to neoplasia buut can be used in inflammatory disease
Describe pustules
- Primary lesion
- Small circumscrimbed elevation of epidermis containing pus
- In dogs usually Staphylococcus intermedius
- May be a feature of sterile, immune-mediated diseases e.g. pemphigus foliaceus
Describe vesicles
- Primary lesion
- Small circumscribed elevation of epidermis containing clear fluid less than 1cm
Describe bullae
- Primary lesions
- Circumsribed elevation of epidermis containing clear fluid larger than 1cm diameter
Outline some causes of vesicles
- Balloon degeneration of keratinocytes e.g. FMD
- Loss of cohesion between cells in or just below epidermis due to antibody response directed at proteins in cellular attachment e.g. bullous pemphigoid
- Cell mediated cytotoxicity leading o a loss of structural integrity of epidermal cells e.g. erythema multiforma
Describe wheals
- Primary lesion
- Localised mast cell degranulation within skin
- Urticaria
- Circumscribed raised lesion consisting of dermal oedema
- Most common in horses
Give some causes of wheals
- Stings
- Venoms
- Insect bits
- Drug reactions
- Allergic reactions
- Physical factors e.g. pressure, cold exercise
Describe scales
- Primary lesion
- Accumulation of loose cornified fragments of epidermis
- Ectoparasites and other chronic skin inflammation may lead to scaling
Describe how scaling occurs
- Normally desquamation of cells from stratum corneum occurs so that cells are not seen
- Accumulation of loose cornified fragments of epidermis
- Often due to increased epidermal turnover
- may reflect priamry defects of keratinisation e.g. idiopathic seborrhoea
Describe comedones
- Primary lesion
- Dilated hair follicles devoid of hair and plugged with keratinous debris (blackhead)
Describe how comedones form
- Processes interfering with hair growth
- Induce defects of keratinisation process in follicular infundibulum
- Most often in dogs
What are some differential diagnoses for comedones?
- Demodicosis
- Endocrine diseases
- Idiopathic seborrhoea
Describe follicular casts
- Primary lesion
- Accumulation of keratinous debris around hair shaft
- Seen protruding from follicular ostium or present when hairs plucked and examined
- Often coexist with comedones
Describe crusts
- Primary lesion
- Dred exudate on skin surface e.g. serum, blood, pus or combination
- Commonly indiseases with pustular component
Describe ulcers
- Secondary lesions
- Break in continuity of epidermis that penetrates the basement membrane
Describe erosions
- Secondary lesions
- Incontinuity of epidermis that does not penetrate the basement membrane
Describe epidermal collarettes
- Secondary lesions
- Circular lesion with circular rim of scale or peeling edge
- Footprint of vesicular or pustular lesion
- Common lesion type in canine pyoderma
Describe scars
- Secondary lesion
- Area of fibrous tissue replacing damaged skin
Describe excoriation
- Secondary lesion
- Erosions or ulceration caused by scratching, biting or rubbing
- Usually seen as consequence of moderate or severe pruritus
Describe fissures
- Secondary lesion
- Linear split through the epidermis to the underlying dermis
- Usually seen as consequence of loss of skin elasticity
Describe lichenification
- Secondary lesion
- Accentuation of skin markings giving elephant skin life appearance
- Associated with chronic inflammation and trauma
- Usually feature of severe and chronic canine allergic disease or Malassezia infection
- WHWT and GSD more prone to this
List types of pigmentation disturbances
- Hyperpigmentation
- Hypopigmentation
- Leukotrichia
What is hyperpigmentation?
Skin pigmentation increased beyond what is normal for that area
What is hypopigmentation?
Skin pigmentation decreased beyong what is normal for that area
What is leukotrichia?
Loss of hair pigment
What is skin pigmentation dependent on?
Nature and amount of melanin within epidermal cells
How does hyperpigmentation often occur?
- Endocrine disease affecting skin
- Consequence of inflammation
How does hypopigmentation often occur?
- Inflammatory processes
- Auto-immune diseases centred on dermo-epidermal junction such as lupus erythematosus
List potential causes of damage to skin
- Microbial
- Ectoparasitic
- Trauma
- chemical
- Allergic
- Autoimmune
- Endocrine/metabolic
- Nutritional
- Environmental
List epidermal responses to damage
- Hyperkeratosis
- Acanthosis
- Lichenification
- Vesicle/pustule formation
- Hyper/hypopigmentation
- Crusting
- Alopecia
List dermal responses to damage
- Erythema
- Oedema
- Thickening
What is hyperkeratosis?
Increased depth of cornified layer (stratum corneum)
What are the different types of scaling?
- Greasy (oleosa)
- Dry (sicca)
Describe the formation acanthosis and hyperkeratosis
- Responses to repeated low grade trauma
- e.g. elbows from lying down
- Leads to release of cytokines from keratinocytes leading to increased division of basal epidermal cells
- Fibroblast proliferation, keratinocyte proliferation, affects division of epidermal basal cells
- Aim is to protect underlying structure
Compare acanthosis and hyperkeratosis
Acanthosis: increased depth fof epidermis
Hyperkeratosis: increased depth of cornified layer
What does lichenification indicate?
Chronic disease
Describe erythema
- Damage leads to release of pro-inflammatory mediators (incl histamine)
- Leads to vasodilation of dermal vessles
- Ultimately leads to erythema
- Common in infectious and allergic processes
- Will blanche
Describe oedema
- Histamin and other cytokines, increased vascular permeability = leakage of tissue fluid
- Pit on pressure
- Classically type I hypersensitivity
Describe dermal thickening
- Associated with longer-standing allergic reactions
- Late phase reaction leading to cellular infiltrate
- Chronic inflammatory conditions
- Sometimes nodular
Describe alopecia
- Loss of hair (partial/complete)
- Failure to grow or damage
What may lead to failure of hair to grow leading to alopecia?
- Endocrine disorders (often bilateral)
- e.g. testicular tumour leading to increased oestrogen
- Nutritional
Give examples of ways hair follicles may be damaged leading to alopecia
- Bacterial pyoderma
- Dermatophytosis (ringworm)
How may different disease elicit similar cellular or tissue responses/signs?
- Signs seen by affecting particular parts of skin
- Set ways in which those parts can respond
- Thus multiple diseases can affect these areas and have similar effects
Discuss the causes of secondary hyperkeratosis
- Non-specific sign
- Increased turnover of epidermis or imbalance between turnover and desquamation
- Metabolic, infectious, parasitic, immune mediated, neoplastic
- Leishmaniasis (protozoal disease), chroic hepatic disease (systemic metabolic disease) and dermatophytosis (fungal infection) for example
Discuss the causes of vesicle formation
- Vesicules usually with viruses (e.g. foot and mouth) or autoimmune disease
- Auto-antibodies attack intercellular proteins leading to separation of keratinocytes
Discuss the causes of pustule formation
- Pustules associated with infection (e.g. bacterial pyoderma Staphylococcus pseudintermedius)
- Can also be sterile e.g. autoimmune diseases such as Pemphigus foliaceus
Discuss the causes of crusting
- Caused by mulitple exudative and ulcerative disease
- Physical damage (mechanical, thermal, chemical)
- Infectious processes (viral, bacterial, fungal and parasitic)
- Sterile inflammatory diseases (autoimmune)
- Ulcerating neoplasms
Discuss the causes of erythema
- Infectious and allergic processes
- Some neoplastic processes e.g. epitheliotropic lymphoma
Discuss the possible causes of oedema
- Type I hypersensitivity
- Pressure and exercise in horses
- Mast cell tumour may lead to histamin release and thus urticaria
List further diagnostic tests for the investigation of skin lesions
- Skin scrapes
- Trichograms
- Cytology
- FNA
- Biopsy
- Microbial culture
- Wood’s lamp examination
Why are further diagnostic tests required in most cases with skin lesions?
- Many diseases will cause similar symptoms
- Required in order to make correct diagnosis and thus provide correct treatment
- Require signalment, history and diagnostic tests
