Dermatitis/Atopic Eczema Flashcards
What is the preferred term:
Dermatitis or eczema?
Eczema - skin lesions with similar clinical and pathological features but different pathogenic mechanisms (i.e: this is an umbrella term)
Acute phase of eczema?
Papulovesicular rash
Erythematous lesions
Spongiosis (oedema)
Ooze or scale and crusting
Difference between scaling and crusting?
Scale - dead keratinocytes
Crust - dried tissue fluid or blood
Chronic phase of eczema?
Lichenification (thickening)
Elevated plaques
Increased scaling
4 main features of eczema?
Pruritic (if it is not itchy, it is not eczema)
ILL-DEFINED (unlike psoriasis)
Erythematous
Scaly
Describe atopic eczema
Genetic and environmental factors cause inflammation of the skin that is most common in childhood
Exhibits type I and IV hypersensitivity and, on histology, shows spongitoic dermatitis
Describe contact allergic dermatitis
Contact of allergen with the skin causes a delayed (type 4) hypersensitivity reaction; this leads to spongiotic dermatitis on histology
Describe contact irritant dermatitis
Non-specific reaction to trauma, e.g: soap, water, leads to spongiotic dermatitis, on histology
NON-ALLERGIC
Describe drug-related dermatitis
Can be a type I or IV hypersensitivity reaction
Histologically, there is spongiotic dermatitis and EOSINOPHILS (unique to drug-related dermatitis)
Describe photo-induced or photosensitive dermatitis
Reaction to UV light causes spongiotic dermatitis
Rash present on light-exposed regions and sparing under clothes
Describe lichen simplex
Physical trauma to skin, such as scratching, leads to thickening of skin, which leads to more itchiness
Histologically, there is spongiotic dermatitis and external trauma
Describe stasis dermatitis
Physical trauma to the skin under hydrostatic pressure, e.g: legs, lower back
Histologically, there is spongiotic dermatitis and extravasation of rbcs (leading to brown pigmentation of skin)
Give examples of allergens in contact allergic dermatitis?
Very common:
Nickel
Chemicals, e.g: in gloves
Topical therapies
Plants
Immunopathology of contact allergic dermatitis?
- Langerhan cells in the epidermis process the antigen (increased immunogenicity)
- Processed antigen is then presented to Th cells in the dermis
- Sensitised Th cells migrate into lymphatics and then to regional nodes where antigen presentation is amplified
- On re-exposure, sensitised T cells proliferate and migrate to and infiltrate skin, leading to dermatitis
What pathological features can be seen in this picture? IMAGE 1
Spongiosis (white spaces between keratinocytes)
Inflammatory infiltrate
Diagnosing contact allergic dermatitis?
PATCH TESTING:
Batteries of allergens placed in small wells and applied to back skin
Left in place for 48-96 hrs, checking at both times
Differentiating between irritant dermatitis and contact allergic dermatitis?
Difficult; the two may overlap or co-exist
5 clinical features seen?
- Erythematous
- Erosions (breaks in epidermis)
- Scaling
- Lichenification (increased skin markings) and hyperlinearity
- Nail dystrophy
Examples of irritant contact dermatitis?
Nappy rash (irritant contact dermatitis to urine) - flexures are spared
Lip-lick dermatitis (to saliva)
How does atopic eczema impact on quality of life?
Very common in children; pruritus leads to sleep disturbance and neurocognitive impairment
This affects the whole family
Describe the itch-scratch cycle
Itchiness leads to desire to scratch; but this causes more itchiness
Features of atopic eczema?
- ILL-DEFINED
- Generalised dry skin
- Flexural distribution but this varies with age; in infants, it often affects the cheeks and abdomen (also, neck flexure and below earlobes) but, as they grow older, begins to affect the flexures
- Assoc. with other atopic disease, e.g: asthma, allergic rhinitis, food allergies
3 chronic changes with atopic eczema?
- Lichenification
- Excoriation
- Secondary infection (gold crusting indicated Staph. aureus infection)
What is eczema herpeticum?
Caused by HSV and SHOULD NOT BE MISSED
Characterised by:
Monomorphic (look the same), punched-out lesions
Systemically unwell child (high fever)
Diagnostic criteria for atopic eczema?
Itching + 3/more of:
Visible flexural rash*
History of flexural rash*
Personal history of atopy (or in a 1st degree relative if under 4 yrs)
Generally dry skin
Onset before age 2 years
*cheeks and extensor surfaces in infants
Treatment of eczema, from mild to severe?
- Plenty of emollients
- Avoid irritants including shower gels and soaps
- Topical steroids
- Treat infection
- Phototherapy – mainly UVB
- Systemic immunosuppressants
- (Biologic agents) - mono/poly clonal antibodies against cytokines in the inflammatory pathway
What is the most important gene in the development of atopic eczema?
Fillagrin
What is discoid eczema?
Scattered, roundish patches of eczema with an unknown cause but is sometimes assoc. with Staph. aureus infection; the rash is WELL-DEFINED making it an exception in eczema
Patients are often atopic
What is chronic actinic dermatitis?
Rare skin condition mainly affecting men >50 years.
Patients are often atopic
Characterised by severely itchy, red, inflamed, and thickened dry skin, mainly in areas that have been exposed to sunlight or artificial light (cut-off at the collar)
What is seborrheic dermatitis?
Chronic or relapsing form of eczema/dermatitis that mainly affects the scalp and face
What is pompholyx dermatitis?
Hand/foot eczema characterised by spongiotic vesicles or bullae (vesicular dermatitis)
What is lichen simplex?
Localised area of chronic, lichenified eczema/dermatitis
Follows repetitive scratching/rubbing due to chronic, localised itch, often on back of head and top of foot ; it is more common in people with anxiety or OCD
What histological features are shown in the biopsy:
a: Spongiosis
b: Inflammatory infiltrate
c: Dermal hyperplasia
d: Epidermal hyperplasia
e: a and b
e
How would you distinguish between irritant and allergic contact dermatitis in this patient:
a: Occupational history
b: Family history
c: Social history
d: Patch testing
e: All of the above
e
What does this patch test result show?
a: Contact allergic reaction to multiple specific allergens
b: Contact allergic reaction to tape adhesive
c: a and b
d: The patient does not have contact allergy
e: Rare ‘blue’ reaction
c
What type of dermatitis does this 6 month old baby have:
a: Allergic contact
b: Irritant contact
c: Atopic eczema
d: Psoriasis
e: Candida (thrush)
b
What has caused this rash and what would you do:
a: Atopic eczema, treat with steroids
b: Contact allergic reaction to nickel, perform patch tests
c: Contact allergic reaction to plastic, perform patch tests
d: Contact allergic reaction to nickel, advise nickel avoidance
e: Irritant dermatitis, treat with emollients
d
What clinical sign gives the clue to the diagnosis:
a: Erythema
b: Scaling
c: Lichenification
d: Cut-off at collar line
e: Grey hair indicating advanced age of patient
d (photosensitivity)
What pattern of eczema does this patient have:
a: Acute
b: Pompholyx
c: Lichenified
d: Infected
e: a and b
e
What infection does this young child have as a complication of their eczema:
a: Fungal – candida
b: Staph aureus
c: Varicella zoster virus
d: Herpes simplex virus
e: b and d
f: It is acute eczema and may not be infected
e
