PATHOLOGY; Classification of skin conditions Flashcards
How many (main) reaction patterns are there?
4.
- Spongiotic intraepidermal oedema (eczema)
- Psoriasiform-elongation of the rete ridges (psoriasis)
- Lichenoid-basal layer damage (liche plants and lupus) - damage to basal epidermis.
- Vesiculobullous-blistering (pemphigoid, pemphigus and dermatitis herpetiformis)
Pathogenesis of psoriasis
> Epidermal hyperplasia and increased epidermal turnover
> Hereditary factors?
> New lesions can arise at sites of trauma
> Complement mediated attack on keratin layer.
COMPLETE PATHOGENESIS IS UNCLEAR
Psoriasis presentaiton
Well defined scaly plaques
Red shiny scale
Picking flakes
Auspitz sign
Extensor surfaces
Psoriatic nail dystrophy
Atypical nail growth and subungual hyperkeratosis
Elongation of the rete pegs
Psoriasis
Become club shaped - bulbous at base
Some fusion of the rete pegs
Lichenoid disorders
Conditions characterised by damage to basal epidermis
Lichen planus
Itchy flat topped violaceous papule
Lichen plans - histology
Irregular sawtooth acanthosis
Hypergranulosis and orthohyperkeratosis
Band-like upper dermal infiltrate of lymphocytes
Basal damage with formation of cytoid bodies
Range of other lichenoid disorders
I> Some resemble lichen planus
- discoid lupus
- some drug rashes
> Others have more marked vacuolar interface change
- examples are erythema multiforme, toxic epidermal necrolysis
- severe EM/ TEN may be life threatening
In lichen planus - what shape does the epidermis form?
Saw toothed.
Keratosis.
Buccal mucosa sign of lichen planus
Wickham’s striae
Immunobullous disorders
Vesicles and bull occur as a secondary phenomenon in many skin diseases e.g. eczema, herpes virus infection, burns
BLISTERS as primary feature.
Pemphigus
Bullous pemphigoid
Dermatitis herpetiformis
Bullous Pemphigus
> Rare autoimmune bullous disease
> Sex incidence is equal, usually middle age
> Loss of integrity of epidermal cell adhesion
> Variable severity
> Responds to steroids
4 distint subtypes
majority PEMPHIGUS VULGARIS
LYMPHOCYTES present
What is happening in pemphigus?
Body is making antibody that are damaging the points of adhesion between the keratinocytes
Can involve oesophagus - can slough their oesophageal lining.
Pemphigus vulgaris?
Autoimmune condition
IgG auto-antibodies made against DESMOGLEIN 3
Desmoglein 3 maintains desmosomal attachments
Immune complexes form on cell surface
Complement activation and protease release
Disruption of desmosomes
Blisters are fragile and burst
End result is ACANTHOLYSIS
Presentation//
- Produces fluid filled blisters which rupture to form shallow erosions
- involves skin esp. scalp, face, axillae, groin, trunk
- may affect mucosa
Desmoglein 3
Maintains desmosomal attachments
What is common to all variants of pemphigus?
Process of acantholysis.
Lysis of intercellular adhesion sites
Desmosomes are cleaved.
Basal layer of epidermis is intact/broken in pemphigus vulgarise?
Preserved as they have different types of attachment
Bullous pemphigoid
Which inflammatory cells are present
> Subepidermal blister
No acantholysis
“Tense” blisters
React with hemidesmosomes that are sticking basal layer to the basal membrane.
Circulating antibodies (IgG) react with a major and or/minor antigen of the HEMIDESMOSOMES anchoring basal cells to basement membrane.
Result is local complement activation and tissue damage.
EOSINOPHILS
Immunofluorescence in Bullous pemphigoid
Linear IgG + complement deposited around basal membrane
Send EARLY lesions for histology
Older lesions of pemphigoid
These show re-epithelialisation of their floor, mimicking pemphigus vulgaris.
Dermatitis herpetiformis
> Rare condition
Autoimmune bullous disease
COELIAC disease
> HLA-DQ2 haplotype
Intensely itchy lesions
- symmetrical
Elbows, knees, buttocks often excoriated
Hallmark is papillary dermal micro abscesses
IgA deposition in dermal papillae
IgA antibodies target gliadin component of gluten but cross react with connective tissue matrix proteins
Immune complexes form in dermal papillae and activate complement and generate neutrophil chemotaxins
Dermatitis herpetiformis is associated with with GI disease?
Coeliac disease
Hallmark of dermatitis herpetiformis
Papillary dermal micro abscesses
Sub epidermal bull formation
Which type of immunoglobulin is deposited in dermatitis herpetiformis
IgA in dermal papillae
What component of gluten does IgA react with?
Gliadin
But cross reacts with connective tissue proteins.
Which antibody is present in pemphigus and pemphigoid?
IgG
Acne vulgaris
Distribution reflects sebaceous gland sites
- face, upper back, anterior chest
Aetiology of acne
- ↑ Androgens at puberty
- ↑ androgen sensitivity of sebaceous glands
- Keratin and sebum plugging of pilosebaceous units (Comedones)
- Infection with anaerobic bacterium, corynebacterium acnes
- Rupture of keratin and sebum build up causes inflammation and foreign body granulomas
Rosacea
Recurrent facial flushing
Commoner in females
Visible blood vessels (eurasia)
Pustules, yellow heads
Perifollicular granulomas
Follcular demodex mites noted
Thickening of skin - rhinophyma
TRIGGERS
- sunlight
- alcohol
- spicy foods
- stress
NOT A TYPE OF ACNE
Is rosacea a type of acne?
NO
Which mite is commonly noted in Rosacea?
Demodex mites
Live in hair follicles
Munro’s micro abscesses
An abscess (collection of neutrophils) in the stratum corneum of the epidermis due to the infiltration of neutrophils from papillary dermis into the epidermal stratum corneum.
They are a cardinal sign of psoriasis
