| Bullous pemphigoid | |
|---|---|
 | |
| A patient present with legs covered in poppedblisters caused by bullous pemphigoid. The blisters cover his entire body. | |
| Specialty | Dermatology  |
Bullous pemphigoid (a type ofpemphigoid) is anautoimmunepruriticskin disease that typically occurs in people aged over 60, that may involve the formation ofblisters (bullae) in the space between theepidermal anddermalskin layers. It is classified as atype II hypersensitivity reaction, which involves formation of anti-hemidesmosome antibodies, causing a loss ofkeratinocytes tobasement membrane adhesion.
Clinically, the earliestlesions may appear as ahives-like red raised rash, but could also appear dermatitic,targetoid,lichenoid, nodular, or even without arash (essential pruritus).[1] Bullous Pemphigoid, is characterized by the subepidermal blisters resulting in tense and less fragile bullae.[2] Tensebullae eventually erupt, most commonly at the inner thighs and upper arms, but the trunk and extremities are frequently both involved. Any part of the skin surface can be involved. Oral lesions are present in a minority of cases.[3] The disease may be acute, but can last from months to years with periods of exacerbation and remission.[4]
Several other skin diseases may have similar symptoms. However,milia are more common withepidermolysis bullosa acquisita, because of the deeper antigenic targets. A more ring-like configuration with a central depression or centrally collapsed bullae may indicatelinear IgA disease.Nikolsky's sign is negative, unlikepemphigus vulgaris, where it is positive.[5]
In most cases of bullous pemphigoid, no clear precipitating factors are identified.[3] Potential precipitating events that have been reported include exposure to ultraviolet light and radiation therapy.[3][6] Onset of pemphigoid has also been associated with certain drugs, includingfurosemide, nonsteroidal anti-inflammatory agents,DPP-4 inhibitors,captopril,penicillamine, and antibiotics.[6]
The bullae are formed by an immune reaction, initiated by the formation ofIgG[citation needed] autoantibodies targetingdystonin, also called bullous pemphigoid antigen 1,[7] and/ortype XVII collagen, also called bullous pemphigoid antigen 2,[8] which is a component ofhemidesmosomes. A different form of dystonin is associated with neuropathy.[7] Following antibody targeting, a cascade ofimmunomodulators results in a variable surge of immune cells, includingneutrophils,lymphocytes andeosinophils coming to the affected area. Unclear events subsequently result in a separation along thedermoepidermal junction and eventually stretch bullae.[citation needed]
Bullous pemphigoid, goes through two distinct phases: The non-bulbous and the bullous phase.[9][2]
Non-bulbous phase, involves mild to severe intractablepruritic skin due to the non-specificity of the disease. involving eczematous orurticarial lesions. This phase of Bullous pemphigoid can occur over the time period of weeks to months.[9][2][10] In the bullous phase, tense blisters form in anannular shape and are filled with clear fluid. This occurs on the abdomen, limbs and lower trunk. Theseblisters average between 1cm-4cm in diameter.[9][2]
Diagnosis consist of at least 2 positive results out of 3 criteria (2-out-of-3 rule): (1) pruritus and/or predominant cutaneous blisters, (2) linear IgG and/or C3c deposits (in an n- serrated pattern) by directimmunofluorescence microscopy (DIF) on a skin biopsy specimen, and (3) positive epidermal side staining byindirect immunofluorescence microscopy on human salt-split skin (IIF SSS) on a serum sample.[12] RoutineH&E staining orELISA tests do not add value to initial diagnosis.[citation needed]
In the early stages Bullous pemphigoid, particularly in rare forms of the disease, it can be misdiagnosed as the lesions may appear more like prurigo simplex subacuta, chronic prurigo, eczema, urticaria and localized.[2][13]
Treatments includetopical steroids such asclobetasol, andhalobetasol which in some studies have proven to be equally effective as systemic, or pill, therapy and somewhat safer.[3] However, in difficult-to-manage or widespread cases, systemicprednisone and powerful steroid-freeimmunosuppressant medications, such asmethotrexate,azathioprine ormycophenolate mofetil, may be appropriate.[3] Some of these medications have the potential for severe adverse effects such as kidney and liver damage, increased susceptibility to infections, and bone marrow suppression.[14] Antibiotics such astetracycline orerythromycin may also control the disease, particularly in patients who cannot use corticosteroids.[citation needed]
The anti-CD20monoclonal antibody rituximab has been found to be effective in treating some otherwise refractory cases of pemphigoid.[15] A 2010 (updated in 2023) meta-analysis of 14 randomized controlled trials showed that oral steroids and potent topical steroids are effective treatments, although their use may be limited by side-effects, while lower doses of topical steroids are safe and effective for treatment of moderate bullous pemphigoid.[14]
IgA-mediated pemphigoid can often be difficult to treat even with usually effective medications such as rituximab.[16]
Bulbous pemphigoid may be self-resolving in a period ranging from several months to many years even without treatment.[3] Poor general health related to old age is associated with a poorer prognosis.[3]
Very rarely seen in children, bullous and non-bullous pemphigoid most commonly occurs in people 70 years of age and older.[3] Its estimated frequency is seven to 14 cases per million per year, but has been reported to be as high as 472 cases per million per year in Scottish men older than 85.[3] At least one study indicates the incidence might be increasing in the United Kingdom.[17] Some sources report it affects men twice as frequently as women,[citation needed] while others report no difference between the sexes.[3]
Many mammals can be affected, includingdogs,cats,pigs, andhorses, as well as humans. It is very rare in dogs; on average, three cases are diagnosed around the world each year.[citation needed]
Animal models of bullous pemphigoid have been developed usingtransgenic techniques to produce mice lacking the genes for the two known autoantigens, dystonin and collagen XVII.[7][8]
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