Pathology of
Common
Dermatitides &
Dermatoses
Mark R. Wick, M.D.
“Papulosquamous” Dermatitides
Defined by clinical attributes,
as slightly elevated papular
eruptions with scaling
 These diseases include
spongiotic, lichenoid, and
psoriasiform dermatitides from
a pathological perspective

“Papulosquamous” Dermatitides:
Common Representative Examples

1.







2.





3.


Spongiotic dermatitides
Contact dermatitis
Eczema (atopic dermatitis)
Superficial mycoses (dermatophytoses)
Seborrheic dermatitis (acute/subacute)
Pityriasis rosea
Selected cases of secondary syphilis
Lichenoid dermatitides
Lichen planus
Lichen simplex chronicus (“neurodermatitis”)
Lupus erythematosus (discoid or systemic)
Dermatomyositis
Psoriasiform dermatitides
Psoriasis vulgaris
ANY CHRONIC SPONGIOTIC DERMATITIS
SPONGIOTIC
DERMATITIDES
Spongiotic Dermatitides:
General Histologic Features

1.

2.

3.
Variable parakeratosis: retention of nuclei
in superficial cornified epidermal cells
Spongiosis: Presence of edema fluid
between individual epidermal cells, which
may progress to formation of vesicles
(microscopic intraepidermal “blisters”)
Inflammation in the epidermis and dermis,
with perivascular dermal accentuation. It
is usually chronic in nature (i.e., featuring
lymphocytes and histiocytes), but small
numbers of neutrophils & eosinophils may
also be observed
Spongiotic Dermatitides:
Histologic Nuances

1.

2.

3.

4.

5.
Allergic Contact Dermatitis: Eosinophils in
the epidermis
Seborrheic Dermatitis: Accentuation of
parakeratosis around
hair follicle ostia, with or
without neutrophils
Pityriasis rosea: Extravasation of red cells
in the epidermis
Dermatophytoses: Neutrophils in the epidermis,
along with intracorneal PMNs;
fungi are visible with the GMS
stain
Syphilis: Spirochetes in epidermis with the
Warthin-Starry/Steiner silver stains
LICHENOID
DERMATITIDES
Lichenoid Dermatitides:
General Histologic Features

1.

2.

3.

4.
Damage to basal epidermal keratinocytes,
with secondary “vacuolar” (clear-cell)
change in their cytoplasm
Infiltrate of lymphocytes + plasma cells in
a “band” beneath the epidermis, with or
without direct involvement of the
dermoepidermal junction
Death of keratinocytes near the stratum
basalis, with formation of “cytoid” bodies
Variable atrophy or hyperplasia
(acanthosis) of the epidermis
Lichenoid Dermatitides:
Histologic Nuances

1.

2.

3.
Lichen Simplex Chronicus: Vertical striation
of collagen surrounding the
rete ridges, in the papillary
dermis
Lichen planus: Irregular “sawtooth”
hyperplasia of the epidermis
with irregular thickness of
the stratum granulosum and
a lack of parakeratosis
Lupus erythematosus/Dermatomyositis:
Atrophy of the epidermis
with thickening of the
epidermal basement
membrane; LE also shows
dermal mucin deposition
PSORIASIFORM
DERMATITIDES
Psoriasiform Dermatitides:
General Histologic Features

1.

2.
3.



4.
5.
Regular acanthosis of the epidermis, but
with suprapapillary thinning
Parakeratosis and/or orthokeratosis
Variable acute inflammation, especially
involving the epidermis & stratum
corneum (“Munro” & “Kogoj”
microabscesses)
Perivascular chronic dermal inflammation
Papillary dermal hypervascularity
Psoriasiform Dermatitides:
Histologic Nuances


1. There are NO specific markers of psoriasis
vulgaris; Munro & Kogoj microabscesses may
be seen in other diseases as well, particularly in
chronic dermatophytoses
2. “Suggestive” histologic features of acute or
subacute spongiotic dermatitis are usually
ABSENT in their chronic forms, yielding
microscopic images which simulate that of
psoriasis closely. Resulting differential
diagnosis includes psoriasis, chronic eczema,
chronic dermatophytosis, and chronic contact
dermatitis
PRIMARY
ACQUIRED
BULLOUS
DISEASES OF
THE SKIN
Primary Acquired Bullous
Diseases of the Skin
Pemphigus
vulgaris
Bullous Pemphigoid
Epidermolysis bullosa
acquisita
Dermatitis
herpetiformis
Primary Acquired Bullous Disorders
of the Skin: Models of Autoimmune
Disease
Disease
Autoantibody Target(s)
 Pemphigus vulgaris Plakoglobin-130kD complex
in epidermal desmosomes
 Pemphigoid
BP antigen in the lamina
lucida of the epidermal BMZ
 Epidermolysis
EBA antigen in sub-lamina
bullosa acquisita
densa
zone of epidermal BMZ
 Dermatitis
Dermal papillary collagen (&
herpetiformis
gliadin/endomysial proteins)
Primary Acquired Bullous Disorders
of the Skin: Histologic Features

1.

2.

3.
4.

Pemphigus vulgaris-- Intraepidermal
blisters, centered
in the suprabasal
region; sparse mixed
acute & chronic
inflammation
Pemphigoid-- Subepidermal blisters, filled
& undermined by PMNs,
eosinophils, & lymphocytes
EBA-- Essentially identical to pemphigoid
Dermatitis herpetiformis-- Dense regional
dermal infiltrates of PMNs,
most notable in upper dermal
papillae & within blisters
Primary Acquired Bullous Disorders
of the Skin: Direct Immunofluorescence
Disease
Pemphigus
DIF Pattern
Intercellular labeling for
IgG, IgM, C’3 in epidermis
Pemphigoid/EBA
Linear labeling of
epidermal BMZ for IgG,
IgM, C’3; collagen type IV
in blister floor in BP & in
blister roof in EBA
Dermatitis
herpetiformis
Interrupted linear/granular
labeling of epidermal
BMZ for IgA, C’3
SELECTED
VASCULAR
ABNORMALITIES
OF THE SKIN
Leukocytoclastic Vasculitis:
Pathologic Features

Synonymous with “small vessel vasculitis,”
“hypersensitivity vasculitis,” or “Zeek’s
vasculitis.” May be associated with
underlying collagen vascular disease,
Henoch-Schoenlein disease, or malignancy.
Microscopic diagnosis is based on:



Neutrophilic infiltration of small venules in dermis, with
karyorrhectic basophilic nuclear “dust” in interstitium
Extravasation of erythrocytes in the dermis
Fibrinoid change in vessel walls is often seen but not
diagnostically necessary
Urticarial Reactions:
Microscopic Features




Principal histologic alteration is dermal edema,
relating to “leakiness” of capillaries in the
corium during reactions featuring local
hyperhistaminosis
Dermal collagen bundles are splayed apart, by
seemingly empty spaces
Variable numbers of eosinophils and
neutrophils are seen around dermal venules &
capillaries
Urticarial vasculitis is defined
histopathologically as an “amalgam” of
urticaria and leukocytoclastic vasculitis