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Blistering disorders

Blistering disorders

Blistering or vesiculobullous disorders constitute a diverse group of conditions in which fluid accumulates in the skin as a result of damage to the epidermis, epidermo-dermal junction or the upper dermis. Although clinical patterns may be very helpful, diagnosis usually requires histology and immunofluorescence. Immunofluorescence requires a fresh specimen in a special medium as stipulated by the laboratory.

Most rare causes of blistering (see Table 1) are not dealt with in these guidelines. The uncommon and rarer causes would usually be dealt with by a specialist.

 Bullous pemphigoid

Bullous pemphigoid is a classic autoimmune disorder with circulating cytotoxic antibodies, which are directed against basement membrane antigens. Its incidence increases with age. It usually presents with tense blisters on an erythematous base. After excluding other causes of bullous diseases such as drugs, bullous impetigo, diabetic bullae and the bullae of renal failure, initial treatment is usually with systemic corticosteroids. A prebullous phase of plaques resembling urticaria or resistant dermatitis also occurs.

Occasionally, potent topical corticosteroids will control or abort localised forms. First-line therapy, to bring the blistering process under control, is

As an alternative (if the patient is old and debilitated with a relative contraindication to high-dose corticosteroids) or in addition to a lower-dose of prednisolone (eg approximately 0.5 mg/kg daily initially), use

If the patient is not responding, the addition of a corticosteroid-sparing agent (eg azathioprine or methotrexate), could be considered. Low-dose oral methotrexate (5 to 12.5 mg per week) monotherapy has also been used successfully.

Management of the blisters includes aspirating large tense blisters and applying wet dressings (see wet dressings) with

Secondary bacterial infection is relatively rare but if present requires appropriate treatment (see Antibiotic therapy - General treatment of dermatitis).

Dermatitis herpetiformis

Dermatitis herpetiformis is a manifestation of gluten sensitivity. Itchy vesicles and bullae on the elbows, knees and lumbosacral region are the hallmarks of this disease. There is granular dermal deposition of IgA antibodies. Gluten-sensitive enteropathy—usually without overt coeliac disease—is always associated.

Institution of a gluten-free diet helps virtually all patients with dermatitis herpetiformis and may enable eventual control without oral medications. Information on a gluten-free diet can be obtained from the Coeliac Society of Australia or a dietitian (see Coeliac disease for more information). However, it is slow to work and the initial treatment of choice to control blistering lesions is dapsone.

Patients with dermatitis herpetiformis are exquisitely sensitive to dapsone, but it needs to be introduced cautiously because of the major adverse effects of haemolytic anaemia, headaches and lethargy. Exclude glucose-6-phosphate dehydrogenase deficiency before initiating dapsone. Leucopenia is not usually a problem because high doses are not continued for long periods.

Initial treatment is

Once the gluten-free diet takes effect, dapsone doses as low as 50 mg on alternate days can give complete control.

Lymphoma involving the gastrointestinal tract is a theoretical remote complication of longstanding dermatitis herpetiformis, as it is for coeliac disease.

Pemphigus

There are 2 main forms of pemphigus: pemphigus foliaceus and pemphigus vulgaris. In both forms there is a split in the epidermis caused by loss of cell-to-cell adhesion and blister formation within the epidermis. The pathogenesis of pemphigus involves a type II hypersensitivity reaction, with circulating autoantibodies cytotoxic for desmosomal components resulting in complement-mediated damage to the desmosomes and loss of cell attachment (acantholysis). Drugs have been implicated in the aetiology (see Table 2).

Pemphigus foliaceus results in acantholysis at a more superficial level and therefore the usual clinical picture is one of crusted scaling rather than visible bullae formation. Mucous membrane lesions do not occur.

Use

If this does not provide adequate control, systemic therapy with moderate-dose corticosteroids may be necessary.

Pemphigus vulgaris may have an acute or very gradual onset of blistering. The most common is a gradual presentation of eroded lesions in the mouth where the disease may remain localised for 6 months or more. Pemphigus vulgaris still causes significant morbidity and some mortality, although this has been greatly reduced by modern treatment. Management is complex and requires specialist care.

Porphyria cutanea tarda

Porphyria cutanea tarda is caused by a deficiency of the enzyme uroporphyrinogen decarboxylase. It is associated with disordered iron metabolism and some patients are heterozygous for haemochromatosis. Often toxic liver damage is the initiating event, usually caused by alcohol, but increasingly by hepatitis B, hepatitis C or human immunodeficiency virus. Patients have increased skin fragility and blisters occur on sun-exposed areas in response to minor trauma. Bullae occur on the backs of the hands, fingers and less commonly the face, and are often associated with scarring.

Patients need to avoid sunlight, alcohol, iron, oestrogens and other hepatotoxins, and undergo regular phlebotomies (unless contraindicated by low haemoglobin levels).

Advise patients to avoid sun exposure when possible, or to wear protective clothing and apply broad-spectrum sunscreens. Reflective sunscreens such as titanium dioxide should be used (for further information, see prevention of sun-related tumours); sunscreens which do not block longer wave ultraviolet A (UVA) and visible light will not be effective. Protective clothing is preferable to sunscreens.

Careful search for exposure to environmental toxins should be considered where alcohol is not the cause. There appears to be a familial tendency, and levels of the deficient enzyme uroporphyrinogen decarboxylase should be assessed in close relatives.

Phlebotomy probably works by increasing consumption of iron and porphyrins in the production of new haemoglobin. Initially, 500 mL of blood is withdrawn every second week, but the frequency can be reduced as the blistering process ceases. Serum ferritin is often raised and its reduction may represent a good indicator of therapeutic effectiveness.

Chloroquine base 77.5 mg twice a week is another form of therapy that is very effective, but is potentially hazardous. It works by increasing urinary porphyrin excretion, and can be used in association with phlebotomy.

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