Dermatitis Flashcards
Hyperkeratosis
Increased thickness of keratin layer
Parakeratosis
Persistence of nuclei in the keratin layer
Acanthosis
Increased thickness of epidermis
Papillomatosis
Irregular epithelial thickening
Spongiosis
Oedema between keratinocytes
Dermatitis
Skin lesions with similar clinical & pathological features but different PATHOGENETIC MECHANISMS (i.e. different causes)
Spectrum of disease.
Acute phase dermatitis
> Papulovesicular
Red (erythematous) lesions
Oedema (spongiosis)
Ooze or scaling and crusting
Chronic phase dermatitis
Thickening (lichenification)
Elevated plaques
Increased scaling
General features of Dermatitis
Itchy
Ill defined
Erythematous
Scaly
In drug reaction-related Dermatitis, what type of cells are present?
Eosinophils
Contact Allergic Dermatitis
One of the most common types of dermatitis
Very common.
- in response to chemicals, topical, therapies, nickel, plants
Gloved hands - why are the back of the hands normally more affected in contact dermatitis?
Skin on the back of the hand is thinner so allergen can penetrate skin faster
Immunopathology of contact allergic dermatitis
> Langerhans cell in epidermis processes antigen
> Processed antigen is then presented to Th cells in dermis
> Sensitised Th cells migrate into lymphatics and then to regional nodes where antigen is amplified
> Specifically sensitised T cells proliferate and migrate to and infiltrate the skin
—> DERMATITIS
Diagnosing contact allergy
Patch testing.
- Batteries of allergens are placed in small wells
- Applied to back skin and left in place for 48 hours
- Reactions checked after 96 hours
IRRITANT contact dermatitis
> Another v common type.
> non specific physical irritation rather than a specific allergic reaction
soap, detergent, cleaning products, water, oil
> Can be difficult to distinguish from allergic contact dermatitis and may CO EXIST
Nappy rash
Irritatn contact dermatitis to urine
Atopic eczema/dermatitis
Itch scratch cycle.
Ill defined erythema and scaling
Generalised dry skin
Flexural distribution
Associated w/asthma, allergic rhinitis, food allergy
At flexures
Some fissuring
What is pathognomonic of atopic eczema?
Scaling/dry skin at the ears.
Behind the ears/ at “flexure”.
Very characteristic
Does your child cry when you pull his top off? (Hitting his ears)
Atopic eczema chronic changes
> Lichenification
Excoriation (erosion caused by scratching)
Secondary infection
What does crusting indicate in atopic eczema?
Staph aureus infection.
Eczema herpeticum
Herpes simplex virus
MONOMORPHIC PUNCHED OUT LESIONS
Child is systemically unwell.
IV antivirals
Fluid resus.
Atopic eczema - diagnostic criteria
Itching +
visible flexural rash hx of flexural rash personal history of atopy Generally dry skin Onset before age 2 years
In infants, what other sites can be affected by atopic eczema?
Cheeks and extensor surfaces
Eczema - treatment
1) Emollients
2) Avoid irritants including shower gels and soaps
3) Topical steroids
4) Treat infection
5) Phototherapy (UVB)
6) Systemic immunosuppressants
7) Biologic agents
Most important gene in atopic eczema?
Filaggrin
Discoid Eczema
Very well defined lesions
Disc shaped.
Scratchingis inducing
Photosensitive eczema
Chronic actinic dermatitis
(cut off at collar is normally a big clue)
Often atopic patients
Other cause of photosensitive eczema?
Secondary to photosensitising drugs
Stasis eczema
Secondary to:
Hydrostatic pressure
Oedema
Red cell extravasation
Seborrhoeic dermatitis
Cradle cap in babies
Nasolabial folds in adults/ adolescents
Pompholyx eczema
Spongiotic vesicles
Vesicles are intensely itchy
Lichen simplex
Scratching
A pruritic eczematous condition resulting from continued rubbing and scratching at a localised area of the skin
assoiciated with a period of anxiety.
Signs - solitary unilateral plaque - fresh coloured pink, hyper pigmented lichenified surface well defined shape
