Pathology Flashcards
Name functions of the skin
- strong barriers to antigens and organisms
- thermoregulation BV and sweat glands
- endocrine function UV stimulation of vitamin D
- protection from UV rays melanin pigment
- immune function langerhans cells
- sensory function; touch, temperature and pressure
Describe the normal epidermis
- stratified keratinising squamous epithelium
- prickle cells prominent desmosomes
- granular layer rich in keratohyalin granules
- corneal layer differentiated keratinised cells
- corneocytes, shed from surface house dust
- melanocytes found in basal layer
- langerhans cells
Describe the dermis
- matrix of type 1 and type 111 collagen
- elastic fibres
- ground substance hyaluronic acid and chondroitin sulphate
- papillary dermis is thin and lies just beneath epidermis
- reticular dermis thicker bundles type 1 collagen
- reticular dermis contains appendage structures- sweat glands, pilosebaceous units
- epidermal BM made of laminin and collagen IV
What is hyperkeratosis?
Increased thickness of keratin layer
What is parakeratosis?
Persistence of nuclei in the keratin layer
What is acanthosis?
Increased thickness of epithelium
What is papillomatososi?
Irregular epithelial thickening
What is spongiosis?
Oedema fluid between squames appears to increase prominence of intercellular prickles. if severe, vesicle filled by oedema fluid develop
Name the four main reaction patterns of inflammatory skin diseases
- spongiotic-intraepidermal oedema eg eczema
- psoriasiform; elongation of the rete bridges eg psoriasis
- lichenoid basal layer damage; eg lichen planus and lupus
- vesiculobullous blistering eg pemphigoid, pemphigus and dermatitis herpetiformis
Describe the pathogenesis of psoriasis
- remains elusive
- new lesions can arise at sites of trauma (koebner phenomenon)
- ?complement mediated attack on keratin layer; munro micro abscesses
- increased epidermal turnover, epidermal hyperplasia
- ?hereditary factors
- ? assoc specific HLA types
What are munro micro abscesses?
Collection of neutrophils in the upper parts of the epidermis
What are lichenoid disorders?
- conditions characterised by damage to basal epidermis
- prototypic condition is lichen planus; common
- itchy flat topped violaceous papules
Describe the histology of lichen planus
- irregular sawtooth acanthosis
- hypergranulosis and orthohyperkeratosis
- band like upper dermal infiltrate of lymphocytes
- basal damage with formation of cytoid bodies
Describe immunobullous disorders
- vesicle and bullae occur as a secondary phenomenon in many skin diseases eg. eczema, herpes virus infection, burns
- immunobullous diseases have blisters as the primary feature
Name some important examples of immunobullous disease
- pemphigus
- bullous pemphigoid
- dermatitis herpetiformis
Describe pemphigus
- rare autoimmune bullous disease
- sex incidence is equal, usually middle age
- loss of integrity of epidermal cell adhesion
- variable severity - occasionally fatal
- responds to steroids
- pemphigus has 4 distinct subtypes
Describe pemphigus vulgaris
- autoimmune condition
- IgG auto-antibodies made against desmoglein 3
- demsogelin 3 maintains desmosomal attachments
- immune complexes form on cell surface
- complement activation and protease release
- disruption of desmosomes
- end results is acantholysis
Describe the appearance of pemphigus vulgaris
- involves skin especially scalp, face, axillae, groin, trunk
- may affect mucosa eg mouth, resp tract. extensive mucosal involvement may be fatal
- produces fluid filled blisters which rupture to form shallow erosions
Describe bullous pemphigoid
- subepidermal blister
- no evidence of acantholysis
- circulating antibodies (IgG) react with a major and or minor antigen of the hemidesmosomes anchoring basal cells to basement membrane
- the result is local complement activation and tissue damage
- dermal papillae project into bulla
What does histology show for bullous pemphigoid?
- immunofluorescence shows linear IgG and complement deposited around the basement membrane
- always send early lesions for histology
- older lesions of pemphigoid show re-epithelialisation of their floor, mimicking pemphigus vulgaris
Describe dermatitis herpetiformis
- relatively rare condition
- autoimmune bullous disease
- strong association with coeliac disease
- associated with HLA-DQ2 haplotype
- intensly itchy lesions symmetrical
- elbows, knees and buttocks often excoriated
- hallmark is papillary dermal microabscesses
Describe the distribution of acne
- distribution reflects sebaceous gland sites
- face, upper back, anterior chest
Describe the aetiology of acne
- increased androgens at puberty
- ?? increased androgen sensitivity of sebaceous glands
- keratin plugging of pilosebaceous units
- infection with anaerobic bacterium corynebacterium acnes
Describe the pathophysiology of acne
- sebum produced by sebaceous gland plugs pilo-sebaceous unit
- keratin and sebum build up to produce comedones (blackheads / whiteheads)
- rupture causes acute inflammation and foreign body granulomas
Describe rosacea
- common condition
- around 10% prevalence in caucasian adults
- commoner in females
- recurrent facial flushing
- visible blood vessels
- pustules
- thickening of skin; rhinophyma
Describe the pathology of rosacea
- vascular ectasia
- patchy inflammation with plasma cells
- pustules
- perifollicular granulomas
- follicular demodex mites often noted
- allergic reaction to mites?
