QuestionSBA
QuestionChoice
The glomerular basement membrane is the kidneys - there will be IgG/C3 deposition in glomerulonephritis (eg. post-infectious)
31816
d
The glomerular basement membrane
QuestionChoice
This is correct. Bullous pemphigoid is an autoimmune condition caused by antibodies against hemidesmosome proteins in the epithelial basement membrane
31813
a
The epidermal basement membrane
QuestionChoice
IgG staining in intercellular space is seen in all types of pemphigus (except IgA pemphigus)
31815
c
Intercellular space
QuestionChoice
Bullous disorders  affect the epidermal layer and basement membrane rather than the dermis
31817
e
The dermis
QuestionChoice
Immunofluorescence will detect IgG and/or C3 on the epithelial cell surface in pemphigus vulgaris
31814
b
Epithelial cell surface
QuestionComment
this is the lowest yield question i have ever seen
11090
User
subscriber
Hypertension Hematoma
QuestionComment
Should spend more time on the wards....
26307
User
subscriber
Al
Concept
Chapter
### Summary

Bullous Pemphigoid and Pemphigus Vulgaris are both autoimmune blistering disorders with different blister locations and antigens involved. The clinical features, investigations, and treatments are similar, with steroids forming the mainstay of treatment. 

### Bullous Pemphigoid

#### Definition

One of the autoimmune blistering disorders characterised by tense subepidermal blisters

#### Pathophysiology

- Autoantibodies targeting the hemidesmosomes that bind the basal keratinocytes of the epidermis to the basement membrane. The antigens are the BP180 and BP230 components of hemidesmosomes
- This causes the development of tense, sub-epidermal blisters that are not readily deroofed
- On immunoflouresence, this produces a linear pattern of immunoflouresence along the basement membrane
- Autoantibodies may also be identified in the circulation
- May sometimes represent a paraneoplastic process, so a careful history and examination is important
- Other associations include drugs (PD-1 inhibitors in melanoma, ACEi and penicillamine), psoriasis treatment (phototherapy), injury to skin, neurological disease, and genetics

#### Clinical Features

- Usually affects older people
- Prodrome of itch, irritation, erythematous, eczematous, urticarial skin changes, followed by tense subepidermal blisters
- Nikolsky's sign is negative
- The mucous membrane's are spared, except for the cicatrial variant (characterised by marked scarring and predilection for the mucous membranes) 

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#### Investigations

- Biopsy for immunoflouresence from lesion edge
- Anti BP180/BP230 antibodies circulating

#### Treatment

- Topical potent steroids at onset of symptoms e.g. itch
- Doxycycline for anti-inflammatory effect
- Systemic steroids (0.5-1mg/kg of prednisolone), continued until no further lesions for one year. Then tapered very gradually over many, many months
- Steroid sparing agents include azathioprine and mycophenolate if relapse during steroid withdrawal
- The cicatrial variant is particularly difficult to treat 

### Pemphigus Vulgaris

#### Definition

One of the autoimmune blistering skin conditions characterised by flaccid intra-epidermal blisters.

#### Pathophysiology

- IgG autoantibodies are targeted against desmosomes, structures that link keratinocytes to other keratinocytes within the epidermis
- The specific antigens are desmoglein 1 and desmoglein 3
- This leads to the development of blisters within the epidermis, which are flaccid and often deroofed
- Immunoflouresence shows a fish-net/chicken-wire pattern of staining within the epidermis
- Drug triggers have been noted (such as ACEi and penicillamine), and it may be associated with an underlying malignancy as a paraneoplastic phenomenon

#### Clinical Features

- Flaccid, thin walled blisters leading to erosions across the body  
- Mucous membranes may be involved
- Nikolsky's sign is positive
- Patients can be quite unwell with pemphigus vulgaris and mortality is high without treatment

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#### Investigations

- Biopsy for immunoflouresence from the edge of the lesion
- Detection of autoantibodies against desmoglein 1 and desmoglein 3 using indirect immunofluorescence (IIF) or enzyme-linked immunosorbent assay (ELISA)

#### Treatment

- Treatment is very similar to Bullous Pemphigoid, with oral predniosolone
- Risk of secondary bacterial infections is high and these often need treating with antibiotics 

### Memory Aid

Pemphigu**s** = **s**uperficial blisters, pemphigoi**d** = **d**eep blisters

Here's a table comparing the two conditions:

|        | Bullous pemphigoid           | Pemphigus vulgaris  |
| ------------- |:-------------:| :-----:|
| Pathophysiology      | IgG antibodies against hemidesmosomal proteins, primarily BP180 and BP230 | IgG antibodies against desmoglein 1 and desmoglein 3|
| Clinical features     | Tense, subepidermal blisters, rarely mucous membrane involvement      |   Painful, fragile blisters and erosions, mucous membrane involvement (oral membranes almost always)|
| Investigation findings | Direct immunofluorescence (DIF) demonstrates linear IgG and complement along the basement membrane zone; Indirect immunofluorescence (IIF) or ELISA detects circulating antibodies against BP180 and BP230      |    DIF demonstrates intercellular IgG deposits in the epidermis; IIF or ELISA identifies antibodies against desmoglein 1 and desmoglein 3 |
Treatment      | High-potency topical corticosteroids for local disease, oral corticosteroids for extensive involvement; immunosuppressive medications (AZT, MMF) for severe or refractory cases | High-dose systemic corticosteroids to induce remission, topical steroids for mucous membranes; adjunctive immunosuppressive agents (AZT, MMF, rituximab) to reduce corticosteroid dependence|



### References
[Bullous pemphigoid - DermNet NZ](https://dermnetnz.org/topics/bullous-pemphigoid)

[Pemphigus vulgaris - DermNet NZ](https://dermnetnz.org/topics/pemphigus-vulgaris)

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An example of pemphigus vulgaris
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An example of bullous pemphigoid.
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Pemphigus and Pemphigoid
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In bullous pemphigoid, IgG and C3 are located at the epidermal basement membrane, indicating an autoimmune response against hemidesmosome proteins.
A patient presents with blistering of the skin. Bullous pemphigoid is suspected. Direct immunofluorescence is carried out and detects IgG and C3 in a linear pattern.

In what location would the IgG and C3 be located to confirm a diagnosis of bullous pemphigoid?
a