Eczema Flashcards
What are these: atopic & infantile seborrheic eczema, irritant & allergic contact dermatitis?
These are the 4x main types of eczema / dermatitis in paediatrics
who does irritant contact dermatitis occur in? (epidemiology)
anyone exposed to sufficient amount of offending agent; more common in those with atopic eczema (diminished skin barrier)
What is the aetiology/cause of irritant contact dermatitis?
irritating substance –> contact –> causes skin inflammation
What is this
rough, dry skin & white scaling with variable erythema caused by low relative humidity (dry) & aggravated by soaps and bathing?
asteatotic eczema
What are asteatotic eczema and nappy rash clinical features of?
irritant contact dermatitis!
How is the diagnosis of irritant contact dermatitis made?
clinical dx
What is the Rx of irritant contact dermatitis?
- emmolients
- topical corticosteroids
- avoidance of irritant
What is the difference between eczema and dermatitis?
both are generic terms for skin inflammation
eczema = endogenous
dermatitis = exogenous
what are these types of:
atopic, venous / gravitational, asteatotic, seborrhoeic, discoid, pompholys, pityriasis alba?
Eczemas!
e.g. endogenous
- *Atopic Eczema
- Venous/ gravitational Eczema
- Asteatotic eczema
- Seborrhoeic dermatitis
- Discoid
- Pompholyx
- Pityriasis alba
What are these types of:
irritant contact, allergic contact, photodermis, eczema herpeticum
= dermatitis types!
e.g. exogenous
- Irritant contact
- Allergic contact
- Photodermatitis
- Eczema herpeticum (vesicles, punched out haemorrhagic lesions, caused in HSV infectino)
What is the aetiology of allergic contact dermatitis e.g. cause?
abnormal immunological response –> inflammation caused by Type 4 cell mediated hypersensitivity to an allergen
~10% of childhood dermatitis
what are nickel, lanolin and urushiol in relation to allergic contact dermatitis?
they can be allergens –> Type 4 cell mediated hypersensitivity
in allergic contact dermatitis
lanolin = sheep wool wax
urushiol = a chemical in some plants
Where does the lesion from allergic contact dermatitis occur?
typically restricted to area of contact
What types of lesion can occur from allergic contact dermatitis & their differences?
- Allergic contact dermatitis –> acute & subacute
-
Acute = really itchy dermatitis –> vesicle and blister formation
- From potent sensitizers e.g. poison ivy
-
Subacute –> linchenification (leathery from itching) and scaling
- from less potent sensitisors e.g. nickel
-
Acute = really itchy dermatitis –> vesicle and blister formation
How do you diagnose allergic contact dermatitis?
- Use HISTORY to identify possible allergen
- PATCH TESTING
How do you manage allergic contact dermatitis?
- emmolients
- topical corticosteroids
- avoidance of the allergen
What is an allergen vs irritant?
irritant is non-allergic
allergy = involves a damaging hypersensitivity immune response by the body to a substance (types 1-4)
What is a type 1 allergic reaction?
Immediate Hypersensitivity (Anaphylactic Reaction)
These allergic reactions are systemic or localized, as in allergic dermatitis (e.g., hives, wheal and erythema reactions)
antigen + membrane IgE of mast cell/basophil
= H2, platelet activating factor, PG and leukotrienes released
What is a type 2 allergic reaction?
Cytotoxic Reaction (Antibody-dependent)
Ab –> ag to induce cell lysis
IgG and IgM mediated e.g. Rh incompatibility
What is a type 3 hypersensitivity reaction?
immune complex reaction
IgG and IgM bind Ag –> PMN releasing tissue damaging enzymes
–> e.g. SLE & chonic infectious diseases e.g. leprosy
What is a type 4 hypersensitivity reaction?
Cell-mediated (delayed hypersensitivity)
reaction initated by T lymphocytes + Ag –> mediated by effector T cells (CD4+ and CD8+) –> 48-72hrs later = cytokines
Which is the most common eczema/dematitis?
Atopic eczema
~15% children
aczema / atopic dermatitis is caused by food allergy
true or false
False
NB: if there is a true food allargy e.g. egg allergy –> immediate peri-oral syx on contact with egg, it is not uncommon for eczema to FLARE up (e.g. its pre-existing eczema) several hours after the allergic reaction
what gene mutations is eczema associated with?
filaggrin gene mutations
[encodes protein that facilitated terminal differentiation of the epidermis and formation of the skin barrier]
What is eczema?
- chronic skin condition
- assoc. w/filaggrin gene mutations
- ==> causes poor barrier function of the skin
- ==> allows IgE sensitisation to air allergens (aero-allergens)
- via the THINNER, PERMEABLE epidermis
What 4 factors can aggrevate eczema & cause a “flare-up”?
- infections
- chemical irritation
- allergy - particularly aero-allergens
- other
What is included in the “other” category for eczema aggravating factors?
-
hot or cold temperatures
- heat
- humidity
- sweat / perspiration from exercising
- food
- stress
- hormones
Sort of infections can cause eczema exacerbations?
- general infection
- or skin infection often induced by scratching
- certain bacteria e.g. staph aureus
- viruses or certain fungi
What sort of chemical irritants can cause eczema exacerbation?
- soap, detergents
- disinfectants (chlorine),
- contact with: chemicals, fumes on job
- juices from:
- fresh fruits
- meats
- vegetables
- juices from:
What kind of allergens can cause eczema flares?
- house dust mites
- animal dander e.g. pets - cats, dogs
- pollens (seasonal)
- moulds
- dandruff
What is the cause of atopic eczema?
multifactorial:
- epidermal barrier impairment
- genetic component - filaggrin gene
- & parts of immune system dysfunctional
- & environmental factors e.g. exposure to allergens in utero or in childhood
What are the clinical features of atopic eczema?
- 1st 6 months of life
- dry itchy rash –> excoriation (abrasion) & linchenfication (leathery-thickening)
- Fhx or Hx of atopy or eczema
Some age groups get atopic eczema most commonly in different parts.
1) extensors, face & trunk
2) flexors
which groups get (1) or (2)?
older children get eczema on flexors
infants get eczema on extensors, face, trunk
What are the complications of eczema and why?
Bacterial infection from the chronic epidermal barrier impairment (filaggrin etc) –> staph aureus infection (lives on skin)
viral infection - due to altered T cell function…
What viral infections can you get due to eczema and what conditions do they cause?
Pox virus –> molluscum contagiosum
Herpes Simplex –> eczema herpeticum (can be FATAL)
What is this?
molluscum contagiosum
(pox virus)
What is this?
Eczema herpeticum
(HSV infection, can be fatal via organ failure if virus spreads to brain, lungs & liver)
How do you diagnose atopic eczema?
- clinical (ask Hx of triggers too)
- plama IgE levels often raised
Why must allergy (oral etc) testing in eczema be based on the clinical history?
if not targeted based on clinical hx:
- you get false positive specific IgE results
- as this is common in eczema & asthma
- this simply reflects exposure and IgE sensitisation in an atopic individual
- TF does not necesserily predict clinical allergy
How many children go onto have eczema in adolescence?
1/3rd
- 2/3rds of children with eczema will recover by adolescence
What are the general measures of management for eczema?
- short nails,
- avoid known exacerbating agents,
- oil/soap substitute
- frequent emollients +/- bandages (with zinc/tar paste/diluted steroids)
What are the topical therapies given for eczema flares?
- topical corticosteroids
- NB: ointment is more effective than cream but messier
What are the oral therapies for eczema flares?
- antihistamines (symptomatic relief)
-
Infection Rx:
- abx e.g. flucloxacillin for 2o bacterial infection
- antivirals e.g. aciclovir for 2o herpes
-
?exclusion diet -
- food allergies may EXACERBATE/flare eczema so investigate and trial an exclusion diet (not cause it, exacerbate)
