This document provides an overview of dermatitis and skin lesion classifications. It begins by defining eczema/dermatitis and discussing the two main classifications of endogenous and exogenous eczema. Major types of dermatitis are then outlined such as atopic dermatitis, contact dermatitis, and stasis dermatitis. The document concludes by describing and providing examples of different primary skin lesions including macules, papules, pustules, vesicles, scales, and scars.

1. CLASSIFICATION OF
DERMATITIS AND
TYPES OF LESIONS

2. Introduction
• ECZEMA IS A GROUP OF SKIN DISEASES
CHARACTERIZED BY IRRITATION AND
INFLAMMATION OF THE SKIN.
• ECZEMA IS A GREEK WORD MEANING ‘TO BOIL’
• SYNONYMOUS WITH DERMATITIS
• INCREDIBLY COMMON

3. • ECZEMA MAY BEINDUCEDBYA WIDERANGE OF EXTERNALAND INTERNAL
FACTORSACTING SINGLYORINCOMBINATION. TWO MAINCLASSIFICATION
ARE:
• ENDOGENOUS ECZEMA: BASEDON AN INHERENTPOTENTIALITYTOHAVE
ECZEMA. NO CONTACT WITHA STIMULUSNEEDED.RECURRENT,SELFABATING
• EXOGENOUS ECZEMA : CONTACT WITHOUTSIDESTIMULANTNEEDED.
CONTACT IRRITANTAND CONTACT ALLERGIC TYPES
Classification

4. MAJOR TYPES OF DERMATITIS
•Atopic dermatitis
•Contact dermatitis
•Dyshidrotic eczema
•Neurodermatitis
•Nummular eczema
•Stasis dermatitis

5.  Atopic dermatitis (AD), also known as atopic eczema.
 It is a type of inflammation of the skin (dermatitis).
 Caused by immune hypersensitivity.
 Results in itchy, red, swollen, and cracked skin.
 Clear fluid may come from the affected areas, which often
thickens over time.
Atopic dermatitis

6. Contact dermatitis
• Red, irritated skin that’s caused by a reaction
to substances you touch.
• It comes in two types:
 Allergic contact dermatitis is an immune
system reaction to an irritant like latex or
metal.
 Irritant contact dermatitis starts when a
chemical or other substance irritates your
skin.

7. Dyshidrotic eczema
Dyshidrotic eczema causes small blisters to
form on your hands and feet.

8. Neurodermatitis
• Neurodermatitis is a skin condition of
canines which is caused by the dog
excessively and obsessively licking spots
on their own body.
• Although allergies, insect bites, and
arthritis may initiate the obsessive licking
that is characteristic of this disorder.

9. Nummular eczema
This type of eczema causes round, coin-shaped spots to
form on your skin.
The word “nummular” means coin in Latin.

10. Stasis dermatitis
 Stasis dermatitis happens when fluid leaks out of
weakened veins into your skin.
 This fluid causes swelling, redness, itching, and
pain.

11. PRIMARY LESIONS
 Macules & Patches
 Papules & Plaques
 Nodules
 Tumours & Cysts
 Pustules
 Vesicles & Bullae
 Wheals
 Scales
 Comedones
 Follicular Casts
 Crusts
• Erosions & Ulcers
• Epidermal Collarettes
• Scar
• Excoriation & Fissure
• Lichenification
• Pigmentation
SECONDARY
LESIONS

12. MACULES AND PATCHES
MACULE: A circumscribed flat area of
change in colour of the skin less than 1 cm in
diameter.
Patch: Same as macule but exceeding
1 cm in diameter.
Macular areas of
hyperpigmentation in a
dachshund with acanthosis
nigricans

13. PAPULES AND PLAQUES
Papule: A small solid elevation of
the skin less than 1 cm in diameter.
Plaque: A large flatter elevation of
the skin, sometimes formed by papules
coalescing. A common example is the
eosinophilc plaque seen in some cats with
allergic skin disease.
Diffuse papular eruption - the
ventrum of a dog with
dermatophytosis
Plaque on the forelimb of a dog
with dermatophytosis

14. NODULES
Nodule: solid elevation of the skin
greater than 1 cm in diameter that usually
extends into the deeper skin layers.
Nodules may result from:
• Neoplasia (originating from skin cells, or metastatic)
• Inflammatory cell accumulation (especially chronic
granulomatous inflammation associated with infections
or sterile processes)
• or less commonly, tissue dysplasia or hyperplasia or
mineral deposition.

15. TUMOURS AND CYSTS
Tumour: A large mass involving
skin structures. The term is often
used in relation to neoplasia but
can technically be used in
inflammatory disease.
Cyst: A cavity with an epithelial lining.
Hair follicle tumour on the
head of a guinea pig

16. PUSTULES
Pustule: A small circumscribed elevation
of the epidermis containing pus.
Pustules in a dog with superficial
pyoderma, complicating dermodicosis

17. VESICLES AND BULLAE
Vesicle: A small circumscribed
elevation of the epidermis containing
clear fluid less than 1 cm.
Vesicle with haemorhagic
contents on the skin of a dog
with a drug reaction
Bulla: Same as vesicle but more
than 1 cm diameter.
Large flaccid bulla on the
abdomen of a dog with
erythema multiforme caused by
a drug reaction

18. WHEALS
Wheal: A circumscribed, raised
lesion consisting of dermal oedema.
Wheal in a horse with acute urticaria

19. SCALES
Scale: An accumulation of loose
cornified fragments of the
epidermis.
Scaling in a dog with cheyletiellosis

20. COMEDONES
Comedo: A dilated hair follicle
devoid of hair and plugged with
keratinous debris (a 'blackhead').
Comedones and alopecia in a Boxer with
generalised demodicosis

21. FOLLICULAR CASTS
Follicular cast: An accumulation of
keratinous debris around the hair shaft
seen protruding from the follicular
ostium or present when hairs are
plucked and examined.
Scaling and follicular casting in a dog with
sedaceous adenitis

22. CRUSTS
Crust: A dried exudate on the skin
surface, either serum, blood or pus or
a combination.
Severe crusting in a dog with
scabies of several months duration
Crusts are commonly seen in diseases with a pustular
component (eg canine pyoderma, pemphigus
foliaceus), and where the exudate from erosions and
ulcers dries on the surface of the lesion.

23. EROSIONS AND ULCERS
Erosion: A break in the continuity of
the epidermis that does not penetrate
the basement membrane.
Ulcer: A break in the continuity of
the epidermis that penetrates the
basement membrane.
Footpad ulceration in a
retriever with
epitheliotropic lymphoma

24. EROSIONS AND ULCERS
Erosions and ulcers can be seen in many
processes. Vesicular and bullous lesions usually
evolve into erosions and ulcers. Ulcers can also
be seen severe infections and in association
with neoplasia (eg squamous cell carcinoma).

25. EPIDERMAL COLLARETTES
Epidermal collarette: A
circular lesion with a circular
rim of scale and or a peeling
edge.
Epidermal collarete lesion in a dog
with a sterile pustular disease
These are 'footprints' of a vesicular or pustular
lesion. They are therefore a common lesion type in
canine pyoderma.

26. SCAR
Scar: An area of fibrous tissue replacing
damaged skin.

27. EXCORIATION AND FISSURE
Excoriation: Erosion or ulceration
caused by scratching, biting or
rubbing.
Severe excoriations in a dog with scabies
Excoriation is usually seen as a consequence of moderate or
severe pruritus.

28. EXCORIATION AND FISSURE
Fissure: Linear split through the
epidermis into the underlying
dermis.
Severe footpad hyperkeratosis
with fissures (arrow) in a dog with
necrolytic migratory erythema
Fissures are usually seen as a consequence of a loss of skin
elasticity. In dogs with the so-called hepatocutaneous
syndrome, footpad hyperkeratosis and fissuring often
leads to lameness.

29. LICHENIFICATION
Lichenification: An accentuation of
the skin markings giving an elephant
skin like appearance
Prominent lichenification in a dog
with chronic atopy
and Malassezia dermatitis
Lichenification is associated with chronic inflammation and
trauma, and is usually a feature of severe and chronic canine
allergic disease or Malasseziainfection, for example. Some
dog breeds seem to develop lichenification more readily than
others; WHWT and GSD often present with this lesion type.

30. PIGMENTATION DISTURBANCES
Hyperpigmentation: Skin
pigmentation increased beyond what
is normal for that area.
Hypopigmentatio: Skin
pigmentation decreased beyond what
is normal for that area.
Leukotrichia: Loss of hair
pigment.
Extensive hyperpigmentation in a
dog with chronic Malassezia
dermatitis