Bullous disease
Overview: - Primary blistering diseases of the skin are rare
- A variety of skin proteins are important in holding the skin together
- Inherited abnormalities or immune damage of these proteins causes abnormal cell separation, inflammation, fluid accumulation and blistering
- Skin biopsy for light and electron microscopy, together with immunofluorescence (IMF) studies, is paramount in diagnosis
One must remember that the most common causes of skin blistering are: - Chickenpox
- Herpes
- Impetigo
- Insect bite reactions
Pemphigus vulgaris Overview: - Is a potentially fatal blistering disease occurring in all races, but it is more common in Ashkenazi Jews
- Onset is in middle age
- Males = females
- Is caused by the development of autoantibodies against desmosomal proteins (dsg3)
Clinical features: - Mucosal involvement (especially oral ulceration) is common and may be the presenting sign in up to 50% of cases
- Is then followed by the appearance of flaccid blisters, particularly involving the trunk
- They tend to become rather itchy
- Blistering usually becomes widespread, but they rapidly denude; thus pemphigus often presents with erythematous, weeping erosions
Treatment: - Very high-dose oral prednisolone (60-100mg daily) or pulsed Methylprednisolone. This may need to be lifelong
- Other immunosuppressants (e.g. azathioprine, cyclophosphamide or cyclosporine) are used as steroid-sparing drugs
- IV immunoglobulin infusions can be useful in resistant cases
- Whilst treatment is normally effective, up to 20% of patients may succumb to either:
- Side-effects of the disease
- Side-effects of the treatment (most common)
Bullous pemphigoid Overview: - More common than pemphigus vulgaris
- Presents in later life (usually over the age of 60 years)
- Mucosal involvement is rarer
- Is caused by autoantibodies against a hemidesmosomal protein
Clinical features: - Large tense bullae appear anywhere on the skin, but often involve:
- They may be centred on an erythematous or urticated background and they can be haemorrhagic
- Pemphigoid can be very itchy
Treatment: - High-dose oral prednisolone (30-60mg daily) and steroid-sparing agents such as azathioprine
- In general, disease control is easier than with pemphigus vulgaris
- Often, treatment can be withdrawn after 2-3 years
Dermatitis herpetiformis Overview: - Is a rare blistering disorder associated with Coeliac disease and, occasionally, other organ-specific autoimmune disorders
Clinical features: - Is most common in males
- Can present at any age but is most likely to appear for the first time in young adult life
- It presents with intensely itchy, small blisters of the skin
- Commonest sites are the:
- Elbows
- Extensor forearms
- Scalp
- Buttocks
- The tops of the blisters are usually scratched off; thus crusted erosions are often seen at presentation
- Remissions and exacerbations are common
Treatment: - Should always be with a gluten-free diet (GFD)
- Control of the skin disease can be obtained with oral dapsone (50-200mg daily) or sulphonamides
- If a strict GFD is adhered to, oral medication can often be withdrawn after 2 years
- The GFD will need to be lifelong – it protects against the rare complication of small bowel lymphoma
Use of dapsone: - Frequently causes a mild dose-related haemolytic anaemia (which is usually well-tolerated)
- The haemolysis can be devastating if there is G6PD deficiency
- Liver damage, a polyneuropathy and aplastic anaemia also occur rarely
- Regular monitoring of a blood count and liver biochemistry is needed
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