Pathology of rashes Flashcards
What are the functions of the skin?
- barrier to antigens/organisms
- thermoregulation
- fluid & electrolyte balance
- endocrine function
- protection from UV
- immune function
- sensory
Which types of collagen are found in the dermis?
Type 1 or type 3
What is the ground substance of the dermis composed of?
Hyaluronic acid & chondroitin
The reticular/papillary contains sweat glands ad pilosebaceous units
Reticular
Which part of the dermis (papillary or reticular) is thickest?
Reticular
What is typical histological feature of a melanocyte?
A clear halo (surrounding a dense purple nuclei)
What is the epidermal basement membrane composed of?
Laminin and collagen IV
Spongiotic oedema causes the prickle cell desmosomes to be stretched. T/F
True
What are the four classifications of inflammatory skin disease?
- spongiotic (intra-epidermal oedema)
- psoriasiform (elongation of rete ridges)
- lichenoid (basal layer damage)
- vesiculobullous (blistering)
Give an example of each of the four classifications of inflammatory skin disease
- eczema
- psoriasis
- lichen planus
- eczema herpetiformis
Describe the pathogenesis of psoriasis.
I would if anyone knew it
Which factors can contribute/exaggerate/trigger psoriasis?
Hereditary HLA type, koebner phenomenon, strep. throat (guttate variety)
What are the histological features of psoriasis?
Parakeratosis and munro microabsesses
What causes munro microabsesses?
Complement proteins attracting neutrophils to the keratin layer
What is the auspitz sign? Which condition is it typical of?
Pinpoint bleeding where the scale of a plaque is rubbed off. Psoriasis
What factors of erythrodermic psoriasis makes it life threatening?
Fluid and electrolyte loss. Risk of infection
How do psoriasis affected nails appear?
Crumbly (but no fungal infection)
Why do nails become more crumbly when affected with psoriasis?
Increased epithelial turnover
Where is acne vulgaris distributed? Which pattern does this follow?
Face, chest and upper back. The distribution of sebaceous glands
What is the pathogenesis of acne vulgaris?
Increased androgens (during puberty) > increased sensitivity of sebaceous glands to androgen > keratin plugging of pilosebaceous units > infection with corynebacterium acnes > bursting causes sebum leakage into the dermis which induces local inflammation
Are cornybacterium acnes aerobic or anaerobic?
Anaerobic
What are the two types of comedones? What is the difference between the two?
Blackheads and whiteheads. Blackheads are open and whiteheads are closed.
How does rosacea present?
Recurrent facial flushing, telangiectasia, pustules, rhinopyma
What is rhinopyma?
Fibrous thickening of the skin of the nose
Who most commonly gets rosacea?
Women and white people
Which factors can aggrevate rosacea?
Alcohol, sunlight, spicy food, stress
Tetracycline medications can be used to treat rosacea. T/F
True - works in some cases
What is the pathogenesis of rosacea?
Vascular ectasia
Patchy inflammation with plasma cells > perifollicular granulomas > pustule formation (follicular dermodex mites often found)
Vesicules/bulla often occur as a secondary phenomenon in many skin diseases. T/F
True
What is the primary feature of immunobullous diseases?
Blisters
Which sex and age groups are most likely to develop pemphigus?
Equal across sexes. Middle aged individuals
What is pemphigus?
An autoimmune bullous condition causing the loss of integrity of epidermal cell adhesion
When is pemphigus most commonly fatal?
When affecting aerodigestive tract.
Which type of autoantibody is involved in pemphigus? What is it made against?
IgG. Desmoglein 3
What is the role of desmoglein 3?
Maintenance of dermosomal attachments
What is the pathogenesis of pemphigus?
Immune complexes form > complement activation > protease release > disruption of desmosomes > acantholysis
How does pemphigus vulgaris present?
Fluid filled blisters which burst to form shallow erosions. Distributed on the skin and mucosal surfaces.
Where on the skin is pemphigus vulgaris most commonly found?
Scalp, face, axillae, groin & trunk
Pemphigus blisters are fragile/strong
Fragile
Which layer of the epidermis is involved in pemphigus vulgaris?
Prickle cell layer
Desmosomes and hemidesmosomes are affected in pemphigus vulgaris. T/F
False - hemidesmosomes are not affected
How can pemphigus be diagnosed? What is the characteristic appearance?
IgG immunofluorescence. Chickenwire pattern
What is bullous pemphigoid?
An autoimmune blistering condition
What is the pathogenesis of bullous pemphigoid?
Circulating IgG antibodies react with major ± minor hemidesmosome antigen > complement activation > local inflammation > subepidermal blistering
A typical feature of bullous pemphigoid is acantholysis. T/F
False - this is a feature of pemphigus vulgaris
How can bullous pemphigoid be diagnosed? What is the characteristic appearance?
IgG immunofluorescence. Linear deposition around the basement membrane
When sending samples of bullous pemphigoid it must be early/late stage blisters. Why?
Early stage. This is because the blisters will mimic pemphigus vulgaris in their later stages
What is dermatitis herpetiformis?
A rare autoimmune bullous disease
What condition is dermatitis herpetiformis associated with?
Coeliac disease
How does dermatitis herpetiformis present?
Highly itchy (often excoriated) symmetrical lesions. Distributed along the elbows, buttocks and knees
Dermatitis herpetiformis is associated with HLA-DQ2 haplotype. T/F
True
What is the characteristic histological feature of dermatitis herpetiformis?
Papillary dermal microabsesses
How can dermatitis herpetiformis be diagnosed? What is the characteristic appearance?
IgA immunofluorescence. Deposits in dermal papilla
What is the pathogenesis of dermatitis herpetiformis?
IgA antibodies target gliaden component of gluten > cross reaction with connective tissue matrix proteins > immune complexes form in dermal papilla > complement activated > neutrophil chemotaxins generated
