Immunobullous disease: Bullous pemphigoid, dermatitis herpetiformis, pemphigus Flashcards

1
Q

What is immunobullous disease?

A

A group of heterogeneous autoimmune diseases characterised by large cutaneous blistering caused by autoantibodies targeting proteins in the epidermis, basement membrane, and dermis.

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2
Q

What is Bullous pemphigoid?

A

A chronic autoimmune cutaneous blistering disease characterised by subepidermal bullae.

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3
Q

What is the typical age of onset for Bullous pemphigoid?

A

70 years old and above.

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4
Q

Is Bullous pemphigoid equally common in men and women?

A

True.

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5
Q

Is Bullous pemphigoid rare in children?

A

True.

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6
Q

What increases the likelihood of drug-induced Bullous pemphigoid?

A

Younger patients.

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7
Q

What are the circulating autoantibodies in Bullous pemphigoid primarily targeting?

A

Collagen XVII (BP antigen 2 BPAG2) and BPAG1.

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8
Q

Where are the antigens targeted by autoantibodies found, in bullous pemphigoid?

A

On hemidesmosomes, which provide adhesion between epidermis and dermis.

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9
Q

Name a type of drug that can induce Bullous pemphigoid.

A

Sulfur-containing drugs like furosemide, sulfasalazine, and antibiotics like amoxicillin and penicillin.

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10
Q

What are the two phases of Bullous pemphigoid?

A
  • Nonbullous phase
  • Bullous phase
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11
Q

Describe the nonbullous phase of Bullous pemphigoid.

A

Urticarial and erythematous patches with pruritus.

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12
Q

Describe the bullous phase of Bullous pemphigoid.

A

Multiple fluid-filled or blood-filled, tense bullae that become flaccid after rupture.

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13
Q

What type of bases do bullae usually have?

A

Erythematous, urticarial bases.

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14
Q

What can bullae heal without, but may leave behind?

A

Scarring but can leave postinflammatory hyperpigmentation or milia/milk spots.

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15
Q

Where are bullae typically distributed in bullous pemphigoid?

A

On flexural surfaces on extremities and trunk, usually not on head and neck.

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16
Q

Can Bullous pemphigoid involve mucosal membranes?

A

Yes, eg. oral mucosa with sparing of the lips.

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17
Q

What is the Asboe Hansen sign?

A

Extension of a large blister to adjacent non-blistered skin occurs when pressure is applied.

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18
Q

What is the Nikolsky sign?

A

Rubbing skin causes the upper epidermis to separate from the lower epidermis.

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19
Q

What is the gold standard for investigating bullous pemphigoid?

A

Direct Immunofluorescence (DIF) microscopy from perilesional skin biopsy, showing linear IgG and/or linear C3 deposits along the dermoepidermal junction.

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20
Q

What assay identifies anti-BPAG2 and anti-BPAG1 antibodies?

A

ELISA assay.

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21
Q

What does tissue biopsy histology reveal in bullous pemphigoid?

A

Subepidermal bullae with eosinophilic infiltrate.

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22
Q

What is dermatitis herpetiformis?

A

A chronic autoimmune cutaneous blistering disease strongly associated with coeliac disease.

23
Q

What is the typical epidemiology of dermatitis herpetiformis?

A

Almost all cases occur with coeliac disease or other gluten-sensitive enteropathy, but can occur without CD.

24
Q

What is the gender prevalence in dermatitis herpetiformis?

A

Overall more common in men, but more common in female children than male children.

25
What is the typical age of onset for dermatitis herpetiformis?
In the 40s, but can occur at any age.
26
Which ethnic groups are more commonly affected by dermatitis herpetiformis?
More common in Caucasians or North Europeans.
27
What autoimmune conditions are commonly associated with dermatitis herpetiformis?
Common: Hashimoto's thyroiditis, insulin-dependent diabetes.
28
What autoimmune conditions are less commonly associated with dermatitis herpetiformis?
Uncommon: Pernicious anaemia, alopecia areata, SLE, sarcoidosis.
29
What genetic predisposition is involved in dermatitis herpetiformis?
Specific HLA genes involved in processing gliadin antigen.
30
What is the pathophysiology of dermatitis herpetiformis?
Genetic predisposition causes IgA autoantibodies to form in response to gliadin and epidermal transglutaminase expressed by keratinocytes, as well as tissue transglutaminase associated with coeliac.
31
What is the clinical presentation of dermatitis herpetiformis?
Bilateral and symmetrical, grouped vesicles and papules that are extremely pruritic.
32
Where are the lesions of dermatitis herpetiformis typically distributed?
On extensor surfaces, upper back, buttocks, and scalp.
33
What do patients usually present with in dermatitis herpetiformis?
Pinpoint erosions and excoriations due to pruritus, with rarely intact vesicles.
34
What is the gold standard for investigating pemphigus?
Direct Immunofluorescence microscopy from perilesional skin biopsy shows discontinuous, granular deposits of IgA selectively localised in the tips of dermal papillae.
35
What assay identifies epidermal transglutaminase (eTG) IgA autoantibodies?
ELISA assay.
36
What test is used for coeliac disease?
TTG test.
37
What does tissue biopsy histology show in dermatitis herpetiformis?
Subepidermal bullae with neutrophilic infiltrate.
38
What characterizes pemphigus?
Group of chronic autoimmune blistering disorders with blisters on the skin and mucosal membranes.
39
What do circulating IgG autoantibodies target in pemphigus?
Desmoglein 3 (Dsg 3) and desmoglein 1 (Dsg 1), which are antigens on desmosomes.
40
What type of split is seen in pemphigus foliaceous?
Subcomeal split.
41
What type of split is seen in pemphigus vulgaris?
Intrapidermal split.
42
What type of split is seen in bullous pemphigoid?
Subepidermal split.
43
What is the clinical presentation of pemphigus vulgaris?
Skin involvement as many flaccid blisters that easily rupture, leaving weeping and crusting erosions; mucous involvement, commonly oral, presents as ulcers.
44
What is a positive sign associated with pemphigus vulgaris?
Positive Nikolsky's sign.
45
What is acantholysis?
Loss of intercellular connections, e.g., desmosomes, causing loss of cohesion between keratinocytes.
46
What are acantholytic keratinocytes?
Round-shaped cells with desmosomal spines, called 'prickle cells'.
47
What does acantholysis cause?
Intrapidermal vesicles to form (clear spaces between acantholytic keratinocytes).
48
What is pemphigus foliaceus?
A rarer form of pemphigus where only Dsg 1 is targeted, resulting in only skin involvement and no mucosal involvement.
49
What are the characteristics of skin involvement in pemphigus foliaceus?
Involves superficial, smaller blisters that quickly rupture to form crusting erosions.
50
What is paraneoplastic pemphigus?
A very rare malignancy-associated disorder characterized by painful oral erosions and a polymorphic inflammatory rash.
51
What is paraneoplastic pemphigus usually associated with?
Usually associated with lymphoproliferative neoplasm.
52
What is the gold standard investigation for pemphigus?
DIF microscopy from perilesional skin biopsy, which shows IgG autoantibodies deposited on the surface of keratinocytes in and around lesions.
53
What does tissue biopsy histopathology show in pemphigus vulgaris?
Intraepidermal vesicles with acantholysis, characterized by a 'chicken-wire' or 'fish-net' appearance.
54
What does the ELISA assay identify in pemphigus?
It can identify if Dsg 3 or Dsg 1 autoantibodies are present to distinguish between forms.