Dermatitis/eczema Flashcards
What is hyperkeratosis?
Increased thickness of the keratin layer
What is parakeratosis?
Persistence of nuclei in the keratin layer
What is acanthosis?
Increased thickness of the epidermis
What is papillomatosis?
Irregular epithelial thickening
What is papillomatosis characteristic of?
Warts (mostly viral)
What is spongiosis?
Oedema between kertinocytes
What histological features are typical of eczema?
Spongiosis and inflammatory cell infiltrate (acute/chronic, lymphocytes &/or neutrophils)
General dermatitis/eczema can be defined as what?
Skin lesions with similar clinical and pathological features but differing pathogenic mechanisms
What is the acute phase of dermatitis characterised by?
Papulovesicular rash, erythematous lesions, oedema, ooze, scaling and crusting
What is chronic dermatitis characterised by?
Lichenification, raised plauques, increased scaling
What is the one universal feature of dermatitis (acute or chronic)?
Itching
How might dermatitis present generally?
Itchy, ill-defined, erythematous, scaly skin lesions
List all the different types of eczema and their corresponding pathogenesis
Contact allergic - type 4 hypersensitivity
Contact irritant - trauma
Atopic - genetic & environmental factors
Drug related - type 1 or type 4 hypersensitivity
Photosensitive - reaction to UV light
Lichen simplex - physical trauma (scratching)
Stasis dermatitis - physical trauma (hydrostatic pressure)
What are the common contact allergies?
Nickel, chemicals, topical therapies, plants
Describe the immunopathology of contact allergy?
Epidermal langerhans cells process antigen > processed antigen is presented to Th cells in dermis > sensitised Th cells migrate to lymphatics and regional nodes > antigen presentation is amplified > re-exposure to antigen causes sensitised T cells to proliferate, migrate and infiltrate skin > dermatitis
How can the allergens causing contact allergy be identified?
Patch testing
What is the time frame for patch testing?
Allergen wells are left on the skin for 48 hours and checked for reaction after 96 hours
What is contact irritant dermatits?
Non-specific physical irritation to some external factor (NOT an immune reaction)
Irritant contact dermatitis may force some patients to change jobs. T/F
True
How is irritant contact dermatitis usually managed?
Avoidance
The incidence for atopic eczema in children is relatively low. Tends to present in early adulthood. T/F
False - tends to present in childhood and disappear by adulthood
How may pruritus be a particular problem in atopic eczema?
Itching causes sleep disturbance which may result in neurocognitive impairment. In young children this tends to put strain on the whole family
The itch-scratch cycle in eczema causes amplified itching. T/F
True
How does atopic eczema present?
- itchy, ill-defined erythematous scaly plaques
- generalised skin dryness
- flexural distribution
- facial distribution in young children
- associated atopy
Where is a common and often overlooked site for the occurrence of eczema in children?
Under/behind the earlobe
What are the chronic changes associated with atopic eczema?
Lichenification, excoriation, secondary infection
What main feature would indicate typical infected eczema?
Crusting (most commonly s.aureus)
How does eczema herpeticum present?
Monomorphic punched out lesions
What is the diagnostic criteria for atopic eczema?
Itching AND 3 or more of:
- visible flexural rash*
- history of flexural rash*
- personal history of atopy (or first degree relative if
How is eczema treated?
- EMOLLIENTS
- avoidance of irritants (soaps)
- topical steroids
- infection treatment if present
- phototherapy (UVB mostly)
- systemic immunosuppressants
What is the most important genetic factor in the development of atopic eczema?
Mutation in the filaggrin gene
What is discoid eczema?
Disk shaped distribution of eczema (pattern of atopic eczema)
How can discoid eczema and psoriasis be differentiated?
Discoid will be a patch while psoriasis will be a plaque
What is chronic actinic dermatitis? What characteristic feature does it usually show?
Photosensitivity dermatitis. Dermatitis cuts off at the collars of shirts/where the skin is covered
Are patients with chronic actinic dermatitis also atopic?
Sometimes (often)
How does stasis eczema present?
In areas of high hydrostatic pressure (i.e varicose veins), oedematous and with red cell extravasation (giving erythema)
What is seborrhoeic dermatitis?
Dermatitis which particularly effects the areas of the skin with a high density of sebaceous glands. In infants - cradle cap. In adolescents/adults - scalp and nasolabial fold
What is pompholyx eczema? How does it present?
Acute eczema. Spongiotic vesicles
What is lichen simplex?
Eczema with no specific disease but caused due to continued scratching (itch-scratch cycle)
