Dermatology 2 Flashcards
Diagnostic sampling, cutaneous reaction patterns, approach to pustules, papules, scale and crust
Outline some special considerations for diagnostic sampling of cutaneous masses
- May not be homogenous esp. if large, incisional wedge or excisional more representative vs punch
- Incisional first if suspect invasive neoplasm
- Ensure biopsy tracts are excised with adequate margins when tumour removed
- Remove deeper tissue “en bloc” and submit untrimmed to look for spread
- Max. 1cm tissue thickness for adequate fixation
Outline some special considerations for bacterial and fungal tissue culture
- Tissue culture more valuable for superficial/deep pyoderma or deep fungal culture vs surface swabs
- Withdraw antibiotics for 5-7 days before sampling for bacterial culture
- Submit punch biopsy sample in sterile saline or sterile saline soaked swab , formalin toxic to bacteria
Describe the method for using a Wood’s lamp
- Only M. canis will fluoresce
- Pre-heat lamp for 5 mins before use, illuminate area of interest in darkened room
- False positives an occur with certain drugs, soaps and bacteria (e.g. Pseudomonas), but these are not associated with hair shafts
- False negatives common
What is the indication for use of a skin biopsy?
To establish a definitive diagnosis that cannot be reached by other, less invasive testing methods, in order to identify or rule out certain conditions
Give examples of key reasons for poor results on skin biopsy
- Samples submitted not representative of lesion
- Primary lesion obscured by secondary lesion
- sample timing inappropriate
- Sample examined not representative of lesion
- Lesion destroyed by sampling
- Unrealistic expectations of biopsy
- Inadequate information given to pathologist
Outline the requirements for attaining good results on skin biopsy
- Be gently
- Biopsy early
- Collect multiple samples representative of range of lesions
- Include crusts
- Biopsy before anti-inflamm. therapy
- Label samples from different areas
- Submit complete history, signalment, description, list of differentials and a diagram
How can the the response pattern to injury be used?
- To formulate list of specific aetiological agents that could cause the lesion
- To suggest categories of disease with similar lesions and common pathogenesis
What is actinic damage?
UV damage
Explain the main disadvantage of pattern analysis of a skin biopsy
- Skin has a limited range of responses, so different disorders may have similar histological appearance
- Diagnosis requires additional information incl. clinical lesion distribution, appearance, duration, location, past medication, other clinical data
Name the 8 patterns that dermatopathologists look for in a skin biopsy
- Folliculitis/furunculosis/sebaceous adenitis
- Perivascular dermatitis
- Vasculitis
- Nodular and/or diffuse
- Interface dermatitis
dermatitis - Intraepidermal/subepidermal Vesicular/pustular dermatitis
- Panniculitis
- Atrophic dermatoses
What is meant by hydropic degeneration?
Vacuoles in stratum basale leading to intrabasal or subepidermal clefts
Describe intracellular oedema
Occurs with hydropic degeneration of basal cells and ballooning degeneration. Seen with herpes virus infections
What is necrolysis?
Epidermal necrosis with no dermal involvement and minimal inflammation
Compare ortho and parakeratosis
- Both are excessive cornification
- In ortho, keratinocytes lose nuclei
- IN para, keratinocytes retain nuclei
What is pigment incontinence?
Release of melanin granules into superficial dermis
What is spongiosis?
Intercellular oedema in the epidermis
What is dyskeratosis?
Abnormal, premature or imperfect keratinisation of keratinocytes
What is epidermolysis?
Degeneration of epidermal basal layer, leading to separation of epidermis from dermis
What hair follicle structures can be affected by inflammation? Give the name of this type of inflammation
- Perifollicular vascular plexus = perifolliculitis
- Follicular wall = mural folliculitis
- Lumen of hair follicle = luminal folliculitis
- Bulb = bulbitis
- Sebaceous glands = sebaceous adenitis
Give examples of diseases that may lead to mural folliculitis
- Pemphigus foliaceous
- Demodicosis
Give examples of disease that may lead to luminal folliculitis
- Demodex
- Dermatophytes
In what condition does bulbitis of the hair follicle occur?
Alopecia areata
What is furunculosis?
Perforating folliculitis with release of keratin into dermis, setting up a marked inflammatory response
Describe the histological appearance of perivascular dermatitis
- Prominent blood vessels
- Oedema of dermis
- Leukocytes around vessels
How is perivascular dermatitis classified, and give the names of the classes
- Classified according to depth
- Superficial dermal
- Mid-dermal/perifollicular
- Deep dermal
What types of cellular infiltrate may occur in perivascular dermatitis and what does each indicate?
- Neutrophil: acute pyoderma
- Lymphocytes: canine atopy
- Eosinophil: type I hypersensitivity, parasitic? Allergic?
Describe the appearance of interface dermatitis
- Cell rich OR cell poor band-like mononuclear infiltrate crossing the dermo-epidermal function (exocytosis)
- Hydropic degeneration of basal keratinocytes
- +/- apoptosis of individual cells, mainly in basal layer (diffusely attacked by lymphocytes or apoptosis induced)
- Pigment incontinent
What is the importance of interface dermatitis?
More specific but more serious pattern compared to perivascular dermatitis, associated with immune mediated disease
Give examples of diseases that would cause an interface dermatitis pattern
- Dermatomyositis
- Erythema multiforme
- Lupoid dermatoses
- VKH (Vogt-Koyanagi-Harada)
What is the most common dermatological diagnostic pattern?
Perivascular dermatitis, but also least specific
Describe vasculitis diagnostic pattern
- Inflammation of blood vessels
- Tight perivascular cuffs of inflammatory cells with degeneration of vascular wall
- Microhaemorrhages
- +/-: panniculitis, dermal necrosis (disturbed blood flow to skin), atrophy of hair follicles
Give examples of diseases that may lead to vasculitits
- Dermatomyositis
- Rabies-vaccine induced panniculitis in dogs
- Pastern dermatitis in horses
- Classical swine fever
- Malignant catarrhal fever
Briefly explain how a post-vaccination vasculitis can develop
- Arthus reaction to vaccination
- Rare, massive accumulation of Ag-Ab complexes depositing in vascular wall, leading to complement activation
- Get alopecic macules
- Type 3 hypersensitivity
How may a diffuse dermatitis pattern occur?
Convergence of nodules, progressive disease
List the cell types that may be present n nodular/diffuse dermatitis and give their aetiologic agent (5)
- Neutrophils: pyogenic agents
- Histiocytes/macrophages: foregin bodies, mycobacteria
- Neutrophils + macrophages: furunculosis, fungi
- Eosinophilic: parasitic
- Lymphocytic: insect bites, vaccine reactions
What are potential underlying causes of vesicles or pustules? (intraepidedermal vesciular/pustular dermatitis pattern)
- Oedema e.g insect bite with acute inflammation
- Intracellular inflammation e.g. blister
- Autoimmune disease attacking desmosomes
Explain the mechanism of vesicle or pustule formation (intraepidedermal vesciular/pustular dermatitis pattern)
- Clefting in the epidermis
- Spongiosis: intercellular pedema in epidermis, epidermal inflammation, parasites, infection
- Acantholysis: infection, autoimmune disease
- Intracellular oedema: mechanism forces
Compare the fluid found in vesicles and pustules
- Vesicular is normal fluid
- Pustular is neutrophilic fluid
How can intraepidermal vesicular/pustular dermatitis be classified?
By position and cellular infiltrate
Describe the positional classifications of intraepidermal vesicular/pustular dermatitis
- Subcorneal: very superficial, e.g. pemphigus foliaceous, pyoderma
- Suprabasilar: deeper, e.g. pemphigus vulgaris
- In follicular external root sheath e.g. pemphigus foliaceous
Describe the classifications of intraepidermal vesicular/pustular dermatitis based on cellular infiltrate
- Neutrophils: bacterial pyoderma, pemphigu foliaceous
- Eosinophils: pemphigus foliaceous, parasitis
Describe the histological appearance of oedema in the skin of a dog
- Intercellular epidermal oedema
- Increased spaced between keratinocytes
- Spines between keratinocytes of stratum spinosum caused by widening of intercellular spaces by oedema
- Remain attached via desmosomal attachment sites
Compare the appearance of pemphigus vulgaris and foliaceous and explain why this difference occurs
- PV characterised by large, confluent ulcers
- PF characterised by erosions and crusts
- Is because acantholysis in PV occurs deeper in epidermis
Compare the prevalence of supepidermal and intraepidermal vesicular/pustular dermatitis
Supepidermal less common
What may cause supepidermal vesicular/pustular dermatitis?
- Autoimmune disease e.g. bullous pemphigoid
- thermal burns
- Severe dermal oedema
- severe interface dermatitis
- May be an artefact
Describe the appearance of subepidermal vesicular/pustular dermatitis
Entire separation of epidermis from dermis
Describe the difficulties associated with subepidermal vesicular/pustular dermatitis
- Difficult to treat and prevent infection of totally exposed dermis
- Loss of fluid
What is panniculitis?
Inflammation of subcutaneous adipose tissue
Give potential underlying causes of panniculitis
- Extension of follicular disease
- Infectious agents
- Vasculitis
- Foreign body
- Pancreatic disease
- Pancreatic carcinomas
- Vitamin E deficiency
- Trauma
What is the most common cause of panniculitis and what does this mean for treatment?
- Often sterile idiopathic, so treat with corticosteroids
- But need to eliminate possibility of infection before use of corticosteroids
What are the potential outcomes of panniculitis?
- Can extend into tissues
- Pain
- Subcut fat can be almost liquefied in severe panniculitis e.g. with pancreatic disease (due to lipases)
What is meant by atrophic dermatosis?
Skin response pattern consisting of atrophy of epidermis, hair follicles, collagen and sebaceous glands. Is not inflammatory, is loss of skin structure due to atrophy.
Describe the histological appearance of atrophic dermatosis
- Orthokeratotic hyperkeratosis
- Follicular keratosis
- +/- calcinosis cutis if HAC
What are the potential causes of atrophic dermatosis?
- Various endocrine causes, require hormone assays to diagnose e.g. HAC, hypothyroidism
- Any chronic systemic disease or malnutrition etc.
- Not inflammation
What are the 3 forms of eosinophilic granuloma complex?
- Eosinophilic granuloma
- Eosinophili plaque
- Indolent ulcer
Where do eosinophilic granulomas usually occur?
- Caudal thighs
- Oral cavity
- Feet
- Can be anywhere
- Occasionally “fat chin”
Describe the appearance of an eosinophilic granuloma
- Well demarcateed, solid, raised, erythematous plaques/nodules
- Eroded or ulcerated surface
- +/- exudation, crust
What are the differentials for an eosinophilic granuloma?
- Neoplasia (SCC, lymphoma, MCT)
- Dermatophytosis
- Feline cowpox
- Cutaneous viral disease
- Mycobacterial infection
- Deep fungal infection
- Bacterial folliculitis, furunculosis, abscess
- Foreign body reaction
- Sterile granulomatous disease
Describe the appearance of an eosinophilic plaque
- Raised, flat topped erythematous plaque
- Usually pruritis
Where do eosinophilic plaques usually occur?
Ventral abdomen, caudal thigh
What are the differentials for eosinophilic plaques?
- Neoplasia (SCC, lymphoma, MCT, metastatic mammary adenocarcinoma)
- Dermatophytosis
- Feline cowpox
- Cutaneous viral disease
- Mycobacterial infection
- Deep fungal infection
Where do indolent ulcers occur?
- Aka rodent ulcers
- Mucocutaneous junction of upper lips
Describe the appearance of indolent ulcers
- Erosive/ulcerative lesion
- Uni or bilateral
- Rarey painful or pruritic
- Possibly associated with pyoderma and a foreign body reaction to intradermal keratin caused by licking
What are the differentials for an indolent ulcer?
- Neoplasia (SCC)
- Trauma
Discuss the role of cytology in the diagnosis of eosinophilic granuloma complexes
- Helpful, esp. re differentiation from neoplasm
- BUT absence of eosinophils does not preclude EGC
- Also, eosinophils may be present with other diseases (mosquito bite hypersensitivity, FHV-1 dermatitis, mast cell tumour)
What are the most likely underlying causes for EGCs?
- Ectoparasites
- Allergies
- Recent information re. pyoderma
Describe the diagnostic approach to eosinophilic granuloma complexes
- Confirm EGC lesion with history, clin. exam, cytology and histopathology
- Investigate underlying cause
Describe the main histological features of an EGC
- Varying degrees of epidermal hyperplasia and ulceration/erosion
- Prominent eosinophilic dermal infiltrate
- Small foci (flame figures) in which collagen fibres are surrounded by degranulation eosinophils seen in all 3 types of EGC
List the treatment options for EGC
- Ciclosporin
- Glucocorticoids
- Hydrocortisone aceponate
- Chlorambucil
- Interferon omega
- Immunotherapy
What need to be done before commencing treatment with ciclosporin for an EGC?
Test for FIV, FeLV and toxoplasmosis and discuss high cost with owner
Outline the most common treatment for EGCs
- Glucocorticoids e.g. prednisolone
- Often down to low dose every other day
Discuss the use of chlorambucil in the treatment of EGCs
- Not licensed in animals but consider in EGC cases that are refractory to steroid therapy
- Can be given with steroids
- Side effects infrequent, but monitor every 2 weeks on haematology
Discuss the use of interferon omega in the treatment of EGCs
- No clinical trials but has been suggested
- Should not be a first line treatment
Discuss the use of immunotherapy in the treatment of EGC
- Expensive
- Owner trained to inject immunomodulating drugs every 2-4 weeks
- Must be imported for needs an SIC
Describe a papule
- Small solid elevation of skin <1cm diameter
- Often erythematous
- My form cruss of serum, pus or blood (papulocrustous lesions)
- Primary lesion
Describe a pustule
- Small <1cm skin elevation filled with pus, often starts as papule
- Primary lesion
- Colour varies: white, yellow, green, red (haemorrhagic)
Where might pustules be located in the skin?
- Intraepidermal
- Subepidermal
- Follicular
What would the presence of many pustules indicate and why?
Deeper lesions as these are less fragile
Describe the appearance of ruptured pustules
- Epidermal collarettes
- Crusts adhered to skin
What is scale?
Rafts of immature keratinocytes which accumulate at the skin surface
What are crusts?
Exudates dried onto the skin
What would bilaterally symmetrical crusts/scale with pinnal involvement be suggestive of?
Autoimmune disease
List the skin diseases causing pustular/papular diseases in dogs, give the most common3 first
1: Superficial bacterial pyoderma
2: Ectoparasites
3: Hypersensitivities
- Fungal infections
- Insect bite reactions
- Autoimmune disorders
- Uncommon disorders
Describe the clinical presentation of superficial bacterial pyoderma causing pustular/papular disease in dogs
- Impetigo
- Folliculitis
- Acne
Give the clinical presentation of ectoparasites that may cause pustular/papular disease in dogs
- Flea bites
- Sarcoptes
- Demodex
Give the clinical presentation of hypersensitivities that may cause pustular/papular disease in dogs
- Flea
- environmental atopy
- Food induced atopy
- contact
Which fungal infections may cause pustular/papular disease in dogs?
Dermatophyosis, Malassezia
Give the clinical presentation of insect bite reaction that gives pustular/papular disease in dogs?
Usually mosquito, usually acute (seasonal)
Give the clinical presentations of autoimmune disorders that may cause pustular/papular disease in dogs
- Pemphigus complex (sterile pustules)
- Bullous pemphigoid
give the clinical presentations of uncommon disorders that may cause pustular/papular diseases in dogs
- Drug eruptions
- Juvenile cellulitis
- Leishmaniasis
- irritant reactions
- Subcorneal pustular dermatitis
- Sterile eosinophilic pustular dermatitis
List the skin diseases that may cause pustular/papular disease in cats, and number the most common
1: Miliary dermatitis
2: Dermatophytosis
- Parasitic
- Superficial bacterial pyoderma
- Allergic
- Autoimmune
- Neoplasia
Describe the clinical presentation of miliary dermatitis in pustular/papular skin disease in cats
Focal/diffuse small erythematous crusted lesions
Describe the clinical presentation of dermatophytosis in pustular/papular disease in cats
Folliculitis, miliary-dermatitis type lesions
Describe the clinical presentation of superficial bacterial pyoderma in pustular/papular disease of cats
- Chin acne
- Folliculitis
- Impetigo
Describe the clinical presentation of allergic skin disease in pustular/papular disease in cats
- Flea
- Atopy
- Adverse food reaction
Describe the clinical presentation of autoimmune disease in pustular/papular disease in cats
Pemphigus complex, esp. pinnae and around teats
Describe the clinical presentation of neoplasia in pustular/papular disease in cats
- Mast cell tumours
- Cutaneous lymphoma
List the causes of miliary dermatitis in cats
- Parasitic
- Allergic
- microbial
- Miscellaneous
- Systmemic disease
Which systemic diseases may cause miliary dermatitis in cats?
FeLV infection, FIV infection, hyperthyroidism
List the “miscellaneous” i.e. not parasitic, allergic, microbial, systemic diseases that can cause miliary dermatitis in cats
- Nutritional deficiencies(EFAs, biotin, generic diet)
- Epitheliotropic lymphoma
- Pemphigus
- Endoparasites (rare)
- Idiopathic
