Dermatitis herpetiformis (DH) and pemphigoid should be recognized as causes of chronic bullous dermatitis.
Patients should be referred to a dermatologist for diagnosis and planning of treatment.
DH-patients must always be referred to investigations to establish possible coeliac disease.
Dermatitis herpetiformis (”skin coeliac disease”)
Diagnosis
Typical vesicles (pictures 12) on erythematous skin, and scratches on the elbows and knees (pictures 12), sacrum, buttocks (picture 3) and scalp.
Ordinary histopathology is usually non-specific, but immunohistopathology is useful.
Coeliac disease should be excluded primarily by measuring transglutaminase antibodies. See Coeliac Disease for details.
Gastroscopy and small bowel biopsy are indicated before starting diet therapy.
Remember to ask about other cases in the family.
Treatment
A gluten-free diet has a favourable effect on the skin symptoms in cases of dermatitis herpetiformis even if the patient does not have coeliac disease. Adequate diet councelling is essential.
Dapsone quickly relieves the skin symptoms but its use bears a risk of haemolysis. Repeated laboratory examinations (monitoring of blood picture as well as liver and kidney function) and clinical follow-up are absolutely necessary.
A specialist should always be consulted on the diagnosis and treatment of dermatitis herpetiformis. In stabile phase, follow up may be done by a general practitioner.
Pemphigoid
Definition
An autoimmune disease of the elderly presenting with vesicles or large bullae. Skin basal membrane antibodies are present.
Symptoms
Pemphigoid affects mainly elderly people (> 60 years of age)
Sometimes starts with a generalized itch.
Large thick-walled, translucent, and itching vesicles or bullae develop on erythematous skin of the trunk and proximal parts of the extremities (pictures 45).
Mucosal surfaces are usually unaffected, but a form restricting solely to the mucosal surfaces is also encountered (picture 6).
The general condition of the patient is unaffected.
Diagnosis
In pemphigoid, over 90% of the patients have anti-basement membrane antibodies that react with the epidermal basement membrane zone (hemidesmosomes). Anti-basement membrane antibodies may already be positive at the itching phase even if actual bullae are not yet seen. The anti-basement membrane antibody test is unspecific and therefore it is recommended to carry out serum anti-BP180 antibody test.
A biopsy should be taken from the side of a fresh (small) vesicle or from an erythematous skin lesion. If a vesicle is biopsied the complete base of the vesicle should be included in the specimen.
The epithelium under an older vesicle has often already regenerated, and interpretation of the histology is difficult. Immunohistology is diagnostic.
A fresh biopsy specimen is required for immunofluorescence (IF) studies. The specimen is put directly into dry ice or liquid nitrogen, or a special container with so-called Michelin transport medium can be used.
Systemic glucocorticoids are the first-line treatment. The dose is individual. The initial dose is prednisolone 0.5 mg/kg/day. Continuous medication is seldom needed.
Treatment with dapsone, as well as adjuvant therapies with glucocorticoids combined with other immunosuppressive drugs or methotrexate is carried out under the responsibility of a dermatologist.
Local treatment with very potent glucocorticoids may suffice in limited disease.
Indications for specialist consultation
Confirmation of the diagnosis and differential diagnosis (immunohistology) are tasks of a specialist. The patient should be referred without delay.
The treatment is best started by a specialist. Often the disease continuously behaves in the same manner in the same patient. After a treatment regime has been found that is the least demanding for the patient it can be repeated under the management of a general practitioner as the disease recurs.