Pemphigoid, Bullous

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Basics

Description

  • Bullous pemphigoid (BP) is a chronic, acquired autoimmune subepidermal blistering skin disorder caused by linear deposition of autoantibodies against the epithelial basal membrane zone.
  • Pruritic, tense, symmetric, localized, widespread bullae, or urticarial plaques
  • Flexural surface (80%), axillary, inguinal folds, and abdomen (20%)
  • Oral lesions develop in 10–20% of cases, rarely affecting mucosae of eyes, nose, pharynx, and anogenital zones.

Epidemiology

  • Most common autoimmune blistering disease
  • Typical between 60 and 80 years old, but juvenile BP can occur
  • Affects both females and males, possibly with higher incidence in females
  • No association with race or geographic location

Incidence
  • BP incidence increases with age (1).
  • 14 to 42 new cases per million per year (2)

Etiology and Pathophysiology

  • Autoantibodies react against hemidesmosomal proteins: the 230-kDa BP antigen (BPAg1) within basal keratinocytes and 180-kDa (BPAg2 or type XVII collagen) in the basement membrane zone (BMZ).
  • IgG is usually the predominant autoantibody leading to C3 complement activation, recruitment of inflammatory cells, and liberation of proteolytic enzymes that break down the dermoepidermal junction.
  • The noncollagenous 16A domain (NC16A) located at the membrane proximal region of BP180 is considered the major target epitope and is recognized in 80–90% of BP patients.
  • It has recently been shown that IgE antibodies correlate with a severe form of BP, and those who test positive for IgE anti-BP180 antibodies required longer duration for remission and therapy.

Genetics
  • Certain class II antigens of the major histocompatibility complex (MHC) alleles DQB1*0301 predominate in the United States.
  • Expression of this allele on antigen-presenting cells is thought to be involved in the presentation to autoreactive T cells in patients with BP.
  • Molecular mimicry has been proposed as a mechanism by which exogenous agents may trigger the immune response.

Risk Factors

  • Advanced age
  • Associated with autoimmune disorders and inflammatory dermatoses like lichen planus, psoriasis, and other forms of bullous disease
  • Increased risk in patients with neurologic disorders such as multiple sclerosis, dementia, stroke, Parkinson disease, demyelinating disorders, epilepsy, depression, and schizophrenia (3)
  • Although drug-induced BP is rare, chronic intake of neuroleptics, aldosterone antagonists, furosemide, dopaminergic drugs, opioids, salicylates, NSAIDs, and phenacetin have been associated.
  • Less frequent: trauma, burns, surgical scars, UV radiation, and x-ray therapy

Commonly Associated Conditions

  • Underlying malignancy can be found in patients with BP, but it may be age related, and the correlation is marginal.
  • Several autoimmune disorders such as rheumatoid arthritis, Hashimoto thyroiditis, dermatomyositis, lupus erythematosus, inflammatory dermatoses–like psoriasis, and lichen planus have been reported but are rare.
  • Increased risk of septicemia, pneumonia, UTI, and pulmonary embolism (3)

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