Immune mediated skin disease Flashcards
What are immune mediated skin disease?
- Immune system fails to tolerate self-antigens
- Mounts response against normal skin component
What’s the difference between primary + secondary IMSD
- Primary IMSD = No external trigger identified (idiopathic)
- Secondary IMSD = Exogenous triggering antigen, most commonly drug, bacteria or virus
What clinical assessment should be done with IMSD?
- Consider signalment (particularly breed) & key historical features
- ID primary lesions
- Consider lesion distribution
- Make differential diagnosis list
- Run tests according to differentials
- Interpret results in line with clinical findings
What are IMSD lesions?
- Pustules - common
- Plaques/nodules - common
- Erythematous macules/patches - common
- Hypopigmented macules/patches - common
- Alopecia
- Vesicles
- Erosions/ulcers - secondary - loss of blood supply, adhesion, self trauma
- Crusts - secondary - pus. exudate, blood (dried)
- Purpura (haemorrhage/bruise)
- Scale
How can you diagnose IMSD?
- Lesion cytology
- Skin biopsy & histopathology
- Haematology, biochemistry, urinalysis
- Diagnostic imaging = radiography, ultrasonography
What are advantages of cytology?
- Easy, cheap, rapid (in house) results - direct impression / FNA
- Differentiate sterile from septic (infectious) disease
- Determine type of inflammation
- May inform management prior to histopath results
What are benefits of skin biopsy + histopath?
- Definitive diagnosis - rule out differentials, determine skin pathology
Case 1 =
Betty = 7yr FN springer spaniel
* Hx = 10wk non-pruritic progressive crusting dermatosis
- reduced appetite last 3 days
* Physical examination =
- General WNL except pyrexia 40oC and
- mild peripheral lymphadenomegaly
* Lesion morphology =
- Thick, yellow adherent crusts, pus under crusts
* Lesion distribution =
- Multifocal
- Dorsal muzzle, periocular, medial pinnae, footpads
What are differentials for pustules?
- Bacterial infection (pyoderma/folliculitis)
- Pemphigus foliaceus
- Superficial pustular drug reaction (rare) - ruled out as not had drugs
- Superficial pustular dermatophytosis (rare)
Betty’s cytology =
- Direct impression smear =
- Needle rupture of intact pustule or
- Below crust after gentle removal
- Microscopy =
- Sterile neutrophilic inflammation and acantholytic keratinocytes +/- eosinophils
- what does this indicate from the differentials?
= Consistent with pemphigus foliaceus
How do acantholytic keratinocytes form with pemphigus foliaceus?
- Auto-antibodies (mainly IgG) target components of desmosomes that link keratinocytes in superficial epidermis
- Separation of KCs > acantholytic ‘rounded up’ KCs
- Neutrophilic inflammatory response > superficial pustules with free floating acantholytic KCs
What are signalment + history indications of pemphigus foliaceus?
- Signalment =
- middle aged (any), predisposed breeds = akita, chow chow, cocker spaniel, dachshund, LR, BBD & SSD (affects many breeds)
- History = variable pruritus, possible drug-trigger (including topical and oral ectoparaciticides)
- Often UV exacerbation
Case 2
Bernie
* Signalment = 6 yr FN Basset hound
* History = 4 yr CAD & Malassezia dermatitis
- ASIT, itraconazole (5-10mg/kg), topical chlorhexidine & miconazole
- Acute onset non-pruritic lumps and discharging tracts
* Physical examination = General WNL
* Lesion morphology =
- 3-8 cm (huge) soft nodules (fixed to dermis)
- Overlying skin normal or erythematous and ulcerated, draining serosanguinous fatty fluid
* Lesion distribution = Trunk and proximal limbs
- What are differentials for plaques + nodules?
- Immune mediated =
- Juvenile sterile granulomatous dermatitis and lymphadenitis (juvenile cellulitis)
- Sterile pyogranulomatous dermatitis and panniculitis
- Feline plasma cell pododermatitis (not a cat)
- Canine eosinophilic furunculosis of the face
- Reactive histiocytosis
- Canine eosinophilic granuloma
- Metatarsal fistulation (of GSD)
- Canine sterile neutrophilic dermatosis (Sweet’s syndrome)
- Canine acute eosinophilic dermatitis
- Cutaneous xanthoma
- Other =
- Neoplasia
- Callus
- Acral lick dermatitis
- Deep infections: mycobacterial, fungal, protozoal
- Arthropod/spider bites
- Foreign body reaction
- Feline eosinophilic plaque or granuloma - not a cat
- Calcinosis cutis/circumscripta
- Sterile pyogranulomatous
- pododermatitis (interdigital furunculosis/interdigital cysts)
What is seen with eosinophilic furunculosis of the face?
- Signalment = young adults
- History = rapid onset, intense pruritus
- Lesion morphology = eroded/ulcerated plaques and nodules
- Distribution = face
- Cytology = eosinophilic inflammation
- Histopathology = eosinophilic folliculitis & furunculosis
What is seen with sterile granulomatous dermatitis + lymphadenitis (juvenile cellulitis)?
- Signalment = puppies (sporadic cases in adults)
- History = acute onset, non-pruritic (painful), pyrexia, lethargy
- Lesion morphology = follicular nodules (furuncules) & plaques (often eroded & crusted), diffuse swelling, alopecia (check for Demodex), lymphadenomegaly
- Distribution = face (muzzle, periocular, pinnae), lymph nodes
- FNA cytology = sterile pyogranulomatous inflammation
- Histopath = sterile perifollicular granulomatous- pyogranulomatous inflammation & furunculosis
What can be done to rule out Ddx?
- FNA cytology - deep infections - mycobacterial, fungal, protozoal
- Skin biopsy + histopath (take extra biopsy + freeze)
On FNA what does sterile pyogranulomatous inflammation
(neutrophils + macrophages) show?
- Sterile nodular panniculitis
- itraconazole can cause IMSD
What are Ddx for hypopigmented / erythematous macules + patches?
- Sterile immune mediated =
- Cutaneous lupus erythematosus
- Erythema multiforme
- Vascular disease (vasculitis / vasculopathy)
1. Familial (GSD, greyhound)
2. Proliferative arteritis of nasal philtrum
3. Proliferative thrombovascular necrosis of the pinnae - Mucocutaneous pyoderma
- Uveodermatologic syndrome
- Anal furunculosis
- Subepidermal blistering dermatoses
- Main non-IM differentials =
- Erythematous macules/patches, wheals = Type I HSR, particularly urticaria, neoplasia
- Erosions/ulcers, crusting = Bacterial & fungal infection, neoplasia (SCC, EL)
- Change in pigmentation = Post inflammatory change, neoplasia (EL)
(epitheliotrophic lymphoma)
What is presentation of cutaneous lupus erythematosus?
- Rapid onset = Vesicular CLE (rare)
- Chronic onset =
- Facial discoid lupus erythematosus (most common variant)
- Generalised DLE (rare)
- Mucocutaneous LE (uncommon)
- Exfoliative CLE (rare)
What is seen with facial discoid lupus erythematosus?
- Loss of cobblestone surface of nasal planum
- Hypopigmented macules and patches
- Erosions, ulcers and crusting of nose
- Black to blue to pink pigmentary change of nose
- Hypopigmentation, erosion, crusting of periocular skin and lips
What is seen with erythema multiforme complex?
- History =
- Acute onset, non-pruritic, +/- systemic signs (pyrexia, lethargy, inappetence)
- Trigger = virus, drug, vaccine, microbial infection, neoplasia, systemic disease, food (can be idiopathic)
- Lesion morphology = pleomorphic
- Primary lesion = annular erythematous macule (target lesions rare in animals)
- Vesicles, bullae, wheals, ulceration, crusts
- Distribution = Ventral abdomen > generalised, mucosae
What is seen with uveodermatologic syndrome?
- Signalment = young to middle aged, Akita predisposed
- History = acute bilateral uveitis, non-pruritic
- Lesion morphology = hypopigmented macules > patches, erythematous macules, erosions, ulcers, crusts
- Distribution = face; nose, lips, periocular skin (occasionally footpads, scrotum, perineum)
What can can immune mediated alopecia?
- Sebaceous adenitis
- Alopecia areata
- Dermatomyositis
- Ischaemic dermatopathy
- Post-injection alopecia
What can cause inflammatory alopecia?
- Bacterial folliculitis
- Demodicosis
- Dermatophytosis
- Leishmaniasis
- Sebaceous adenitis
- Alopecia areata
- Dermatomyositis
- Ischaemic dermatopathy
What can cause non-inflammatory alopecia?
- Endocrinopathies
- Cyclical flank alopecia
- Telogen/anagen defluxion
- Paraneoplastic alopecia
- Post-clipping alopecia
- Congenital alopecias
- Follicular dysplasias
- Pattern alopecia
- Colour dilution alopecia
- Post-injection alopecia
What is seen with sebaceous adenitis?
- Signalment = standard poodle, Akita, vizsla
- History = non-pruritic unless SBI
- Lesion morphology = partial alopecia and poor coat quality, follicular casts and scale
- Distribution = generalised
- Cytology = no significant findings unless SBI
- Histopath = pyogranulomatous inflammation targeting sebaceous glands > destruction of sebaceous glands and hair follicle atrophy
What is seen with alopecia areata?
- History = non pruritic, chronic onset
- Lesion morphology = focal to multifocal, partial to complete patches of alopecia +/- erythema and hyperpigmentation
- Distribution = head/face
- Histopath = lymphocytic destruction of hair bulbs
What is seen with dermatomyositis / ischaemic dermatopathy?
- Signalment = young collies, SSD, PWD, Beauceron shepherd, Belgian shepherd
- History = non-pruritic, chronic course +/- myositis
- Lesion morphology = focal to multifocal alopecia, variable hyperpigmentation, hypopigmentation, scaling, erosion/ulceration & crusting
- Distribution = face and extremities (dorsal digits, pinnae & tail tips, nails)
- Histopath = chronic dermal & vascular inflammation > follicular atrophy +/- myositis (include muscle in biopsy)
How would you manage IMSD?
- Removal/treatment of any external triggers =
- Drugs
- UV light = sunscreen
- Confirmed (via blood work/imaging) internal disease including infections
- Food = perform elimination diet for relapsing disease - Control of inappropriate immune response =
- Baseline haematology, biochemistry, urinalysis
- Immunosuppressive/immunomodulatory drugs = topical for mild/localised disease, combination for severe / relapsing disease (generally more effective and better tolerated)
- Sebaceous adenitits = also need to replace epidermal lipids
