Bullous disease Flashcards
What are the 3 main autoimmune bullous skin diseases?
- Bullous phemphigoid
- Pemphigus
- Dermatitis herpetiformis (DH)
Define what bullous phemphigoid is
It is an autoimmune condition causing subepidermal blistering of the skin
Describe the pathogenesis of bullous phemphigoid
- IgG antibodies react against hemidesmosomal proteins BP180 & BP230. These proteins are associated with hemidesmosomes which are structures responsible for anchoring basal cells to the basement membrane
- Resultant local complement activation & tissue damage ensues leading to the development of a subepidermal blister
Who is mainly affected by bullous phemphigoid ?
- Often presents in people > 60
- Uncommon in younger people
Describe the distribution of bullous phemphigoid
- It is usually widespread on the trunk & limbs, but in 15-30% it may be localised.
- Uncommonly mucosal lesions may be present - most commonly the mouth (mouth usually spared tho)
What are the clinical features of bullous phemphigoid ?
- Itchy erythematous plaques & papules may be presenting feature (pre-bullous development)
- Severly itchy, tense fluid-filled blisters typically around the flexures
- Blisters rupture forming crusted erosions
- Blisters heal without scarring
- Blisters are Nikolsky sign negative
What is shown in this pic ?
bullous phemphigoid - shows large tense bullae
What is Nikolsky sign?
This is dislodgement of the superficial epidermis by a shearing force
How is bullous phemphigoid diagnosed ?
1st line = skin biopsy + direct immunofluoresence (DIF)
What is the immunofluoresence appearance of bullous phemphigoid ?
Shows IgG & C3 at the dermoepidermal junction (green line in pic)
What is the treatment of localised bullous phemphigoid ?
Topical corticosteroids (ultra-potent e.g. Clobetasol propinate)
What is the treatment of generalised bullous phemphigoid ?
Oral steroids (prednisolone) + methotrexate + antibiotics (tetracycline - mainly doxycyline + dapsone)
What is the prognosis of bullous phemphigoid ?
Most patients achieve remission within 3-6months
What is the main type of pemphigus accounting for 80% of cases ?
Pemphigus vulgaris
What is pemphigus vulgaris ?
It is a rare autoimmune disease that is characterised by painful blisters & erosions on the skin & mucous membranes - most commonly inside the mouth
Who is usually affected by pemphigus vulgaris ?
Usually affects middle aged people (30-60) & most common in Ashkenazi jewish populations
Describe the distribution of pemphigus vulgaris
- Most commonly arise on upper chest, back, scalp & face (axillae & groin)
- 80% will have oral mucosal lesions & erosions (may also have erosions of vulvula, conjunctivae, pharynx, larynx, oesophagus & rectum)
Describe the pathogenesis of pemphigus vulgaris
Keratinocytes are cemented together at sticky spots called desmosomes. In pemphigus vulgaris IgG antibodies are directed against a protein called desmoglein 3 found in desmosomes. This results in acantholysis & the formation of intra-epidermal fluid-filled blisters
Define what acantholysis is
Acantholysis = breakdown of intracellular adhesion sites, such as desmosomes resulting in loss of connection between keratinocytes
What are the clinical features of pemphigus vulgaris ?
- Skin lesions appear as flaccid thin walled fluid-filled bullae/vesicles
- Lesions easily rupture leaving raw, denuded (stripped) erosions
- Lesions are Nikolsky sign positive
- Oral mucosal erosions (superficial blistering & erosions widespread within mouth, painful, slow to heal ulcers)
What is the likely cause shown here ?
Pemphigus vulgaris
What is the likely bullous disease shown ?
Pemphigus vulgaris
What is the likely bullous disease shown ?
Pemphigus vulgaris
What is the immunofluoresence appearance of pemphigus vulgaris ?
- Shows IgG on the surface of keratinocytes creating chiken-wire pattern (recall this is the green lines)
- Acantholysis seen
Describe the pathogenesis of DH
- Gluten triggers production of IgA antibodies & an autoimmune process that targets the skin & gut.
- Regarding the skin the result is development of sub-epidermal blisters
What are the clinical features of DH ?
- Lesions often appear in groups/clusters
- Characteristically small blisters on an erythematous urticarial base
- Blisters are very itchy with rash usually preceeding blister formation
- Blisters are often eroded & crusted due to scratching
- Excoriations (lesions following trauma)
- mucosal membrane lesions are rare
What is shown in this pic ?
DH
What is shown in this pic ?
DH
What is shown in this pic ?
DH
What is shown in this pic ?
DH
What is the immunofluoresence appearance of DH ?
Shows IgA deposition in a granular pattern in the upper dermis
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Go over the levels of blistering
