Immunobullous diseases are uncommon chronic skin disorders caused by autoantibodies directed against different cutaneous proteins. This chapter covers bullous pemphigoid, pemphigus vulgaris and dematitis herpetiformis. These disorders primarily occur in older adults and can cause significant discomfort in affected patients. They can even be fatal in the case of pemphigus. Patients with immunobullous diseases often have significant quality of life issues related to physical, emotional and mental health.1 Skin biopsies for routine histology and immunofluorescence are needed to confirm the diagnosis.
Blisters are more commonly seen in non-immunobullous conditions such as contact dermatitis, bullous impetigo, herpes simplex, herpes zoster, and bug bites. These are covered in the last table.
Bullous pemphigoid (BP) is an uncommon autoimmune blistering eruption which primary affects elderly patients. Its incidence increases with age, with the mean age of onset ranging from 64 to 80 years of age.2 It is more common in those with pre-existing neurological diseases, such as dementia, Parkinson's disease, stroke, epilepsy, and multiple sclerosis.3
The incidence is estimated to be between 2.5 and 42.8 new cases per million per year,2 and may be increasing over time.4 Many studies have shown a slight female predominance; however, this may be due to the increased percentage of females in the elderly population. After 80 years of age, it is more common in males.2
Bullous pemphigoid is an autoimmune disease associated with the production of autoantibodies targeting the basement membrane zone (BMZ) (Figure 19-1). The BMZ is important for the adhesion of the epidermis to the dermis, and so when targeted, leads to a separation (blister) in this space. The antigens themselves are parts of the hemidesmosomes of the basal cells. The targets are BP 180 and BP 230.5 BP 180 is a transmembrane protein also known as type 17 collagen. BP 230 is a cytoplasmic (intracellular) plakin family protein. There is evidence for the pathogenic roles of these autoantibodies in this disease, especially against BP 180. More recently, eosinophils have been shown to play a large role in bullous pemphigoid, which has had treatment implications.6
Schematic of the basement membrane zone demonstrating the location of BP 180 and BP 230. The basement membrane zone allows for adhesion of the epidermis to the dermis.
Additionally, several medications have been shown to be associated with the development of bullous pemphigoid. In particular, aldosterone antagonists, dipeptidyl peptidase-4 inhibitors, anticholinergics, and dopaminergic medications are associated with the development of bullous pemphigoid and should be carefully prescribed, especially in elderly patients with neurologic conditions.7