autoimmune bullous lesions of skin- in brief

1. IMMUNE MEDIATED BULLOUS
LESIONS OF SKIN
BY EKTA JAJODIA

2.  Blister – fluid filled cavity within or beneath the epidermis
VESICLES
( <0.5cm in diam)
BULLAE
(>0.5cm in diam)
PATHOLOGICAL EVELUATION
Approach to diagnosis-
1. Anatomical level of split/blister separation plane
2. Mech. of blister formation
3. In case of subepidermal blisters – presence/absence of
inflammation, pattern and specific cell types involved

3. ANATOMICAL LEVEL OF SPLIT
 Blister may form at any one of four diff levels-
1. Subcorneal/intracorneal
2. Within spinous or malphigian layers
3. Suprabasilar
4. Subepidermal

4. MECHANISM OF BLISTER FORMATION
1. SPONGIOSIS – Accumulation of ECF within epidermis with
resultant separation of keratinocytes
Stellate appearance of keratinocytes
2. ACANTHOLYSIS – Loss of keratinocyte cell-cell contact
 Keratinocytes are rounded with condensed cytoplasm, large nuclei,
peripheral condensation of chromatin and prominent nucleoli
 Acantholytic cells are viable

5. 3. RETICULAR DEGENERATION (Ballooning degeneration) –
intracellular edema with secondary rupture of keratinocytes and its
death
 Desmosomal attachments connects strands of ruptured
keratinocytic membrane to intact keratinocyte – gives irregular
meshwork appearance to epidermis
4. CYTOLYSIS – disruption of keratinocytes- occurs when high
levels of friction/heat damages structural matrix(keartin) and
desmosomes
5. BASEMENT MEMBRANE ZONE DISRUPTION

6. AUTOIMMUNE BULLOUS DISEASES -
TARGET ANTIGENS
DISEASE TARGET ANTIGENS
Pemphigus foliaceus Desmoglein 1
Herpetiform pemphigus Desmoglein 1
IgA pemphigus(SPD type) desmocollin 1
IgA pemphigus(IEN type) Desmoglein 1 or 3
Pemphigus vulgaris Desmoglein 3
Epidermolysis bullosa acquisita Type VII collagen

7. DISEASES TARGET ANTIGENS
Paraneoplastic pemphigus Desmoglein1,3
Desmoplakin 1,2
Bullous pemphigoid BPAg1(230kDa)
BPAg2(180kDa)
Pemphigoid gestationis BPAg2(180kDa)
Dermatitis herpetiformis Tissue transglutaminase
Linear IgA bullous dermatosis LABD97
Ocular cicatricial pemphigoid plectin
Cicatricial pemphigoid BPAg2, epiligrin
Deep lamina lucida pemphigoid 105kDa
Anti-p200 pemphigoid 200kDa

8. PEMPHIGOUS GROUP
 Acantholysis – mech. of bulla formation here
 Divided into 5 types-
1. P. vulgaris – reactive form is P. vegetans
2. P. foliaceus – lupus like variant- P. erythematosus
Endemic variant – folo selvagem
3. IgA pemphigus
4. Drug induced pemphigus
5. Paraneoplastic pemphigus

9. PATHOPHYSIOLOGY
 Target Ags of P. are located in desmosomes which are
prominent adhesion molecules
 Desmosome complex contains-a.
Transmembrane constituents – desmoglein(DSG) and
desmocollins (DSC)
b. Cytoplasmic constituents – plakoglobin(PG), plakophilin(PP)
and desmoplakin(DP)
 ECD of transmembrane constituent form dimers with adjacent
cell
Cytoplasmic domain of transmemb. constituent bind to PG

10. This PG links intermediate filaments (keratins) to desmosome via
DP
DESMOSOME COMPLEX

11.  ECD of DSG and DSC are targets for Abs
 DSG1 – expressed in upper layers of epidermis
If Abs form- skin lesions occur
No mucous membrane lesions
 DSG3 – expressed in deep layers of epidermis and mucous
membrane
If Abs form- oral lesions with or without skin lesions occur

12. DISEASES TARGET ANTIGENS
P. vulgaris- 1.mucosal mainly
2. mucocutaneous
DSG3
DSG1 and 3
P. foliaceus DSG1
PNP DSG1,3 and DP
IgA pemphigus- 1. SPD type
2. IEN type
DSC1
DSG1 and 3

13. PEMPHIGUS FOLIACEUS
 Recurrent crops of flaccid bullae that easily rupture – so shallow
erosions and erythematous plaques
 Initially in face and trunk – then spreads to involve large areas of
body
 Mucous membrane involvement is rare
 Target Ag – DSG1
Ab – IgG4 subclass
 2 types- a. lupus like – P. erythematosus
b. endemic variant - fogo selvagem(wild fire)
 Develops in those who lives near rivers- its said that a black
fly(simulium) may be a cause

14. Pemphigus : foliaceus
erythematous
: vulgaris
: vegetans
SUPERFICI
AL
DEEP

15. HISTOPATHOLOGY
 Earliest change – formation of vacuoles in intercellular spaces in
upper layers of epidermis – these expand leading to cleft formation
 Late lesions – epidermis- hyperplastic with parakeratosis and
orthokeratosis
 Superficial bulla with split high in granular layer or just beneath
stratum corneum
 Dyskeratotic cells with hyperchromatic nuclei – distinctive feature
of granular layer
 Bulla contains fibrin, neutrophils and scattered acantholytic
keratinocytes (no bacteria present)

16.  Superficial dermis is edematous with mixed inflammation with
both eosinophils and neutrophils
 Direct immunofluorescence – intercellular staining for IgG and
C3 in both affected and normal skin
 Indirect immunofluorescence – demonstrates circulating
antibodies in nearly 90% of non endemic cases

17. 2. Subcorneal blister c/o neutrophils and acantholytic cells
3.Dyskeratotic hyperchromatic granular cells are diagnostic
4. IgG deposited in upper layers of epidermis

18. PEMPHIGUS VULGARIS
 Target antigen DSG3 in only mucous lesion
 In case of mucocutaneous DSG3 and 1 both
 Abs are predominantly IgG4 subclass
 Initial lesion is oral blister with ulcers and erosions – weeks to
months later cutaneous lesions
 In addition to oral lesions , other mucosal lesions may develop -
conjunctiva, larynx and rarely esophagus, urethra, vulva, vagina
HISTOPATHOLOGY - earliest changes- edema and
disappearance of intercellular bridges of keratinocytes in lower
epidermis

19.  Established lesions – suprabasal bullae with acantholysis
 Basal cells lose their intercellular bridges but remain attached to
dermis giving a tombstone appearance
 Blister cavity contains acantholytic cells with some eosinophils
and neutrophils
 Dermal changes are usually mild, superficial mixed
inflammatory cell infiltrate
 No histological difference between drug induced P. vulgaris
from idiopathic cases
 Immunostaining with monoclonal Ab 32-2B – detects DSG 1
and 3 – patchy pattern of staining seen in idiopathic cases and not
in drug induced type
 DIF – demonstrates IgG in intercellular regions of epidermis

20. The earliest changes consist of
intercellular edema with eosinophilic
spongiosis leading to loss of
intercellular bridges in the lower
epidermis
SUPRABASAL
BLISTER
The suprabasal blister contains few acantholytic cells, neutrophils and
eosinophils. Note the dermal papillae lined by a single layer of basal
keratinocytes, so-called villi

21. Lace like
intercellular space
deposition of IgG
PV – suprabasilar
PF – subcorneal/within
granular layer

22. IgA PEMPHIGUS
 Intraepidermal vesicobullous eruption
 Most common sites are axilla and groin. Can involve trunk and
proximal extremities
 Mucous membranes are usually spared
 2 types-
1. Subcorneal pustular dermatosis (SPD) type
2. Intraepidermal neutrophilic(IEN) type – lesions with central
crusts and peripheral vesiculation- so called sunflower lesions
 target Ags – in SPD type – DSC 1
in IEN type – DSG 1and 3

23. HISTOPATHOLOGY
 In SPD type – sub corneal pustules with mild acantholysis
 In IEN type – intraepidermal pustules
 Underlying dermis shows mild inflammatory cell infiltrate
 DIF – Intercellular deposition of IgA in epidermis
 In SPD type – increased intensity of staining in upper epidermis
 In IEN type – IgA staining is throughout the entire epidermis
 IgG is present in small number of cases – known as IgA/IgG
pemphigus

24. SPD – subcorneal
pustule
Neutrophils and fibrin in
blister cavity

25. PARANEOPLASTIC PEMPHIGUS
 Characterized by polymorphous skin lesions with features of both
erythema multiforme and pemphigus vulgaris in association with
internal neoplasms, esp. NHL
 Other ass. are Hodgkin's disease, thymoma, hepatocellular
carcinoma, MFH, castleman’s disease, etc
 PNP can precede diagnosis of malignancy, particularly in patients
who develop castleman’s disease, or it may develop many years after
development of tumor
 7 clinical variants are recognized -
1. Erythema multiforme-like (vacuolar interface dermatitis)
2. pemphigoid-like (subepidermal blister)
3. Pemphigus-like (suprabasilar blister)

26. 4. GVHD-like
5. Lichen planus pemphigoid/ lichen planus like (lichenoid
inflammation)
6. Cicatricial pemphigoid-like
7. Linear IgA dermatosis-like
 Poor prognosis
 3 or more Abs are present in same patient-
1. DP 1 ,2
2. Envoplakin
3. DSC 2 ,3
4. DSG 1 , 3
5. Periplakin
6. Plectin

27.  Abs against DSG 3 are IgG 1 or 2 ( in P.vulgaris against DSG3 is
IgG4)
 Autoantibodies may get deposited in skin, lungs, and other organs
and may produce damage to these organs. Known as “paraneoplastic
autoimmune multiorgan syndrome”(PAMS)
 Treatment is aimed at underlying malignancy to control the
autoantibody production
HISTOPATHOLOGY -
 Lichenoid tissue reaction/ interface dermatitis with extension of
infiltrate into reticular dermis
 Mostly lymphocytes but occasional eosinophils and neutrophils
 Suprabasal acantholysis and clefting may be seen
 DIF – Intercellular and BM staining with C3 and IgG

28. Lichen planus like
(lichenoid tissue reaction)
and P. vulgaris like
(suprabasal blister)
Both intercellular and BM
staining with IgG

29. SUBEPIDERMAL BLISTERS
 To understand this , it is essential to have some knowledge of
epidermal basement membrane zone(BMZ)
 From epidermis to dermis – 4 distinct components of BM
1. Basal keratinocyte plasma membrane
2. Lamina lucida
3. Lamina densa
4. Sublamina densa zone – including anchoring fibrils
BASAL KERATINOCYTE PLASMA MEMBRANE
 Plasma membrane incorporates hemidesmosomes
 Components of hemidesmosomes-
1. Intracellular component – Major bullous pemphigoid
antigen(BPAg1) / 230 kDa and plectin

30. 2. Transmembrane component – Minor bullous pemphigoid antigen
(BPAg2)/180kDa and α6β4 integrin
 Abs to BPAg1 – in bullous pemphigoid
 Abs to BPAg2 – in bullous pemphigoid
pemphigoid gestationis
cicatricial pemphigoid
linear IgA bullous dermatoses
 Abs to β4 of α6β4 - ocular cicatricial pemphigoid
 Mutation of β4 - junctional epidermolysis bullosa

31. LAMINA LUCIDA
Weakest link in dermal-epidermal junction (DEJ) – so easily
severed
 M/L Ags ass with lamina lucida – laminin 5, 6, 1
uncein
nidogen
 defect in this Ags are common in Epidermolysis bullosa

32. LAMINA DENSA
 main component is type IV collagen
Consist of 6 different chains alpha 1-6
 Other components are- laminin1, nidogen, precelan

33. SUBLAMINA DENSA ZONE
 Main component is anchoring fibrils(AF) which tether epidermis
to papillary dermis
 AF are composed of type VII collagen and laminin 332
 Abs to type VII collagen seen in – EBA
Bullous SLE

35. SALT-SPLIT SKIN IMMUNOFLUORESCENCE
 Variant of indirect immunofluorescence
 Normal skin from a normal person is taken and soaked in 5ml
NaCl
After 24hrs , the salt solution induces a subepidermal blister in the
normal skin at the level of lamina lucida
Indirect immunofluorescence done- patient’s serum directed against
the salt-split skin

37.  IgG Abs go above the split (epidermal side) in BP
 IgG Abs go below the split (dermal side) in EBA

38. B- Bullous pemphigoid; C - EBA

39. SUBEPIDERMAL BLISTERS
INFLAMMATORY CELLS DISEASES
With litle inflammation EB
With lymphocytes PNP
With eosinophils BP
Pemphigoid gestationis
With neutrophils DH
Linear IgA bullous dermatosis

40. EPIDERMOLYSIS BULLOSA ACQUISITA
 Non inflammatory subepidermal bullae develop in areas
subjected to minor trauma such as extensor surface of limbs
 Target antigen – EBA antigen which is a 290 kDa type VII
collagen – a major component of anchoring fibrils
HISTOPATHOLOGY-
 classic form – non inflammatory subepidermal blisters
 bullous pemphigoid like – inflammatory blisters – mostly
lymphocytes and neutrophils
 PAS stain- BM is split and most of the PAS positive material
are in blister roof

41.  DIF – linear deposition of IgG / C3/ C5 along BM zone
 A useful clue to the presence of Abs targeting type VII collagen
is presence of u-serrated pattern of linear IgG deposition
 Routine DIF cannot distinguish between EBA and bullous
pemphigoid
 SALT-SPLIT SKIN TECHNIQUE – Abs bind to dermal floor,
deposited below lamina densa
 Fluorescence overlay antigen mapping (FOAM) technique – can
be used to determine site of deposits

42. Non inflammatory
subepidermal bulla Serrated deposition of
IgG in blister base

43. BULLOUS PEMPHIGOID
 Most common subepidermal blister
 Occurs primarily in elderly
 M/L tense bullae develop on normal or erythematous skin
 Oral lesions seen in 10-40% , but involvement of other mucosal
areas is rare
 May occur in childhood – two types
1. Infantile BP – in 1st yr of life – in acral areas
2. Localised vulval BP- confined to vulva only
 Many clinical variants – 1. vesicular pemphigoid
2. Pemphigoid vegetans
3. Polymorphic pemphigoid
4. Pemphigoid excoriee

44. 5. Drug induced pemphigoid
6. Pemphigoid nodularis
 Target antigens – BPAg1/230 kDa and BPAg2/180kDa
 Abs are – IgG4 and IgG1
 Abs to BPAg2 is more associated with oral lesions, less responsive
to steroids and poor prognosis
HISTOPATHOLOGY-
 Unilocular subepidermal blisters
 cell rich type – blister develop on erythematous skin - eosinophils
predominant cell in blister cavity and in dermis – more than in
arthropod bite reaction
 cell poor type – blister develop on normal skin – scant
perivascular lymphocytic infiltrate with few eosinophils

45.  In lesions of several days duration - blister may appear
intraepidermal at its periphery as a result of regeneration
‘Caterpillar bodies’ – segmented , eosinophilic, PAS positive
globules arranged in linear array in roof of blisters – feature of
porphyria cutanea tarda – sometimes seem in BP
 DIF – linear , homogenous deposition of IgG/C3 along BM
 Salt-split skin technique- deposition found on the epidermal side
of the blister

46. FIGURE 9-16. Bullous pemphigoid. (A) Prebullous phase, eosinophils are present at the
dermoepidermal junction and in the dermis. (B) Cell-rich variant, subepidermal blister
formation and an inflammatory infiltrate composed predominantly of eosinophils and a
few neutrophils in the dermis and bullous cavity. (C) Cell-poor variant, subepidermal
blister with few inflammatory cells.

47. Vesicular pemphigoid. There is a small
subepidermal blister
subepidermal blister, the lumen
of which contains eosinophils

48. Bullous pemphigoid. The
basement membrane
zone shows a linear
pattern of staining for C3.
Salt-split skin IF – deposits on
the blister roof (epidermal
side)

49. PEMPHIGOID GESTATIONIS
 aka herpes gestationis
 rare, pruritic, vesicobullous dermatosis of pregnancy and
puerperium
 occasionally seen in association with hyadatidiform mole or
choriocarcinoma
 onset is in 2nd or 3rd trimester
 Subside within several weeks of delivery
 diagnosis can be made by commercially available BP180 ELISA
 Rarely neonate develops vesicular lesions due to transfer of
maternal BP180 autoantibodies
 IgG1 class Ab (pemphigoid gestationis factor) is formed against a
placental antigen – this cross reacts with BP180 antigen of BM

50. HISTOPATHOLOGY
 Early lesion – marked edema of papillary dermis
 Superficial and mid dermal infiltrate by lymphocytes, eosinophils
and histiocytes
 Infiltrate is predominantly perivascular in location
 Established blister – is subepidermal , contains similar
inflammatory infiltrate within the cavity
 Eosinophilic microabscesses may be formed in dermal papillae
DIF – Linear pattern of IgG or C3 in BM zone
Salt split skin – deposits in epidermal side

51. Pemphigoid gestationis. There is subepidermal
clefting with both neutrophils and eosinophils in the
dermal infiltrate

52. LINEAR IgA BULLOUS DERMATOSES
 Subepidermal blistering disorder
 2 clinical variants –
1. Chronic bullous dermatosis of childhood
2. Adult IgA bullous dermatosis
 Target Ag – 97 kDa Ag ( degradation products of
180kDa/BPAg2
 Chronic bullous dermatosis of childhood – in 1st decade of life
/ large tense bullae/ perioral or genital regions/ polycyclic
grouping known as ‘cluster of jewels’ sign
 Circulating IgA Abs are present in 70% of childhood disease
and in 20% of adult cases

53. HISTOPATHOLGY –
 Subepidermal blisters with neutrophil as predominant cell
 Indistinguishable from DH by presence of papillary
microabscesses and neutrophils in light microscope
 DIF – homogenous linear pattern of IgA deposition along BM
zone of non-lesional area
Subepidermal blister with neutrophils in the lumen and in
the base

54. DERMATITIS HERPETIFORMIS
 Subepidermal blistering disorder – intensely pruritic papules and
vesicles – bullae are uncommon
 Ass. with high incidence of gluten sensitive enteropathy – in 90%
cases and also with internal cancers, esp intestinal lymphoma
 Target Ag – tissue transglutaminase (tTG)
 sites- elbows, knees, shoulders, nape of neck
 onset – early adult life
 Gluten free diet – reversal of villous atrophy and skin lesions /
also protective effect against development of lymphoma
 IgA Abs formed in gut binds with skin transglutaminase(TG)
 In skin 6 TG isoenzymes are present

55.  Deposits mainly seen are IgA/TG3 aggregates in small blood
vessels in papillary dermis
 This complex activates complement – chemotaxis of neutrophils
in papillary dermis
 Also serum levels of IL-8 increases - increases the expression of
CD11b on neutrophil cell surface – increase neutrophil function –
enzymes released by these neutrophils destroy two BM components
(laminin and type IV collagen) – formation of blisters
HISTOPATHOLOGY –
 Early lesions – collection of neutrophils and occasional
eosinophils at tips of dermal papillae – papillary microabscesses
 Fibrin is also present at the tips of dermal papillae – imparting a
necrotic appearance

56.  In lesions of 36-48 hrs – neutrophil fragmentation occurs
 Very rarely intraepidermal neutrophils occur – confusion with
IgA pemphigus
 In older lesions – subepidermal vesiculation occurs
 Initially multilocular blisters due to interpapillary ridges – but
after few days these attachments break down – formation of
unilocular blister
 Distinction between DH and linear IgA bullous dermatosis is
impossible histologically
 Older lesions may resemble BP – eosinophils more predominant
in the latter condition

57.  DIF – Granular / fibrillary/ thready deposits of IgA in dermal
papillae of perilesional and uninvolved skin
 Deposition is greatest in normal skin adjacent to an active lesion
 If DIF testing is negative – repeat test – negative results of DIF
testing of 2 appropriately selected biopsy sites are strong
indication that patient does not have DH

58. Dermatitis herpetiformis. A- There is a subepidermal
blister , B/C- A microabscess is present in a dermal
papilla
A- linear deposition of IgA along BM in linear IgA dermatosis
B- granular deposits of IgA in the dermal papillae in DH

60. DERMATITIS
HERPETIFORMIS

62. PEMPHIGUS
FOLIACEUS