Immunology, Allergy + Derm Flashcards
Anaphylaxis represents the most severe end of the allergy spectrum and can potentially have fatal results.
What are the clinical features of anaphylaxis?
- Respiratory → Laryngeal oedema, leading to upper airway obstruction + stridor, and bronchospasm leading to lower airway obstruction and wheeze
- GI → Abdo cramping, nausea, vomiting, diarrhoea
- CVS → Hypotension, tachycardia, shock
- Skin → Urticaria, agioedema
How is diagnosis of anaphylaxis made?
- Life-threatening emergency requiring prompt treatment
- Diagnosis based on history + clinical presentation
- Levels of tryptase, proteinase contained in mast cell, can support the diagnosis
- It is measured as treatment begins and again within 1 to 4 hrs
What is the acute management of anaphylaxis?
- Resuscitate the patient using ABCDE approach
- Remove offending allergen if possible
-
Adrenaline should be administered immediately + repeated after 5 minutes if no response
- Child >12yrs → 500 micrograms IM (0.5mL of 1:1000)
- Child 6-12yrs → 300 micrograms IM (0.3mL of 1:1000)
- Child <6yrs → 150 micrograms IM (0.15mL of 1:1000)
- Following resuscitation, for all established cases of anaphylaxis, give:
- Chlorpheniramine → anti-histamines important for ameliorating rapid release of histamine by mast cells
- Hydrocortisone → use of a corticosteroid will suppress immune response + may prevent late-phase response
What is the long-term management of anaphylaxis?
- Allergen avoidance is key in preventing future episodes
- The patient should undergo skin prick testing + immunoassay testing for IgE to specific allergics if there is doubt
- Prescription of an Epipen (under supervision of allergy clinic) will provide some security in case of further anaphylaxis
Eczema refers to a group of conditions characterised by itchy, dry and inflammed skin. Atopic eczema is the most common type in children, affecting 20% of children in the UK. It results from impaired barrier function and usually starts in infancy. In those with atopic eczema, the risk of later developing asthma and hay fever is increased.
What are the clinical features of eczema and its two patterns/types?
- Presents w/ dry, erythematous, itchy skin
- Increased skin temp, oedema, weeping + crusting
- Infantile eczema → affects face, neck, scalp + extensor surfaces; nappy mostly spared; majority clear within few months but may progress
- Childhood eczema → favours flexural surfaces, antecubital + popliteal fossae, volar aspect of wrists, necks + ankles; less weepy + wet than infantile; marked lichenification
What is the management of eczema?
- Establish diagnosis, severity + extent of disease
- Good education vital: give written + verbal advice to parents, explain atopic eczema is a chronic condition + aim of treatment is adequate control, explain recognition + management of flare ups
- Determine + avoid exacerbating factors: stress, environment allergens, irritants
- Maintain skin hydration w/ generous + repeated applications of emollients
- Stop soaps + shower gels and use substitutes
- Topical corticosteroids to minimise inflammation - steroid phobia major issue
- Treat pruritus using antihistamines
- Initiate prompt + aggressive treatment of secondary infection w/ Abx or antivirals as appropriate
- 2nd line Rx → topical calcineurin inhibitors, bandages + stockinette garments
- 3rd line → phototherapy, methotrexate, cyclosporine, azathioprine
What are the complications of eczema?
- Post-inflammatory hypo/hyperpigmentation
- Bacterial infection (common) → staph aureus + strep pyogenes; cause golden crust + pulsation (impetiginized eczema); mild localised infection treated w/ antiseptic washes + topical antibacterial ointments
-
Viral → chickenpox infection widespread + severe; molluscum contagiosum more common in children w/ eczema + spread by scratching
- Eczema herpeticum serious complication of HSV - presents w/ monomorphic clusters of vesicles that erode + crust; prompt diagnosis + Rx w/ systemic aciclovir is paramount; same day dermatology referral highly recommended
What are causes of nappy rash?
- Irritant dermatitis
- Candida dermatitis
- Seborrhoeic dermatitis
- Psoriasis
- Atopic eczema
What are general management points for nappy rash?
- Disposable nappies preferrable to towel nappies
- Expose napkin area to air when possible
- Apply barrier cream (eg Zinc + castor oil)
- Mild steroid cream (eg 1% hydrocortisone) in severe cases
- Candidal nappy rash → topical imidazole; cease use of barrier cream until candida settled
Irritant contact dermatitis
- Causes?
- Clinical features?
- Treatment?
- Caused by: prolonged contact of urine w/ skin, diarrhoea, infrequent changing, using non-disposable nappies
- Moist erythematous patches
- Blisters + ulcers in severe cases
- Affect butocks, perineum, top of thighs + lower tummy
- Inguinal folds spared
Rx → freq nappy changing + use of disposable nappies; protective emollients; topical corticosteroids
CANDIDA INFECTION
- Causes?
- Clinical features?
- Management?
- Organsim = Candida albicans causing candida dermatitis
- Precipitated by compromise of cutaneous barrier eg. irritant dermatitis
- Erythematous patches, may involve inguinal creases + flexures
- Characteristic satellite lesions
- Scaling at the margins of lesions
Rx → topical antifungals eg. imidazole
ATOPIC DERMATITIS
- Causes?
- Clinical features?
- Management?
- Genetic predisposition to develop hypersensitivity reactions to common env allergens
- Presents after first 2 months of life
- ITCHY!
- Excoriated areas → erythematous, weeping, crusted
- Face + trunk predominantly affected
- Child’s skin tends to be dry
Rx → avoid irritants (soap, bio detergents); liberal application of emollients; topical corticosteroids
INFANTILE SEBORRHEIC DERMATITIS
- Causes?
- Clinical features?
- Management?
- Unknown cause
- Normally presents in first 2 months
- Erythematous, non-itchy, scaly eruption on scalp
- develops into thick, yellow adherent layer AKA cradle cap
- scaly rash can spread to face, behind ears, flexures + napkin area
Rx → emollients; topical corticosteroids if widespread body eruptiion; ointment containing low conc of sulphur + salicylic acid for scalp; antifungals may be of some use
What is Henoch-Schonlein purpura?
- IgA vasculitis
- an IgA mediated autoimmune disease
- overlap w/ IgA nephropathy (Berger’s disease)
- precipitated by infections + vaccinations
- classically affects children 3-10yrs old
- more common in boys
What are clinical features of Henoch-Schonlein purpura?
- Purpuric rash → characteristic raised purpuric rash, over buttocks + extensor surfaces of limbs; child usually clinically very well
- Arthralgia → pain, particularly in knees + ankles, occasionally associated w/ periarticular oedema; usually responds well to simple analgesia
- Abdo pain → this can also be due to intussusception, which is a complication of the disease
Usually seen in children following an infection and may be features of IgA nephropathy also eg. haematuria, renal failure
What is a capillary hemangioma?
- AKA strawberry naevi
- benign tumours of vascular endothelium
- Occur within first few months of life
- Grow rapidly in first year of life + then gradually regress
- Involution occurs in around half by 5 years and in majority by 9 years
What is erythema toxicum neonatorum?
- migratory raised erythematous rash
- overlying papules or pustules
- normally appears on day 2 or 3 of life
- resolves spontaneously after three to five days
What is milia?
- AKA milk spots
- White papules present at birth
- Nose + cheeks
- Caused by build-up of keratin + sebaceous material in skin follicles
- Benign skin lesions + resolve in first few weeks of life
What is a mongolian blue spot?
- Blue pigmented macules that present at birth
- Most commonly occur in the sacral gluteal region
- Lesions can be large
- Have higher incidence in darker pigmented skin
- Benign lesions + tend to fade within first 2 years of life
What is naevus simplex?
- Benign pink, blanching macule present in newborns
- AKA “salmon patch” or “storker’s bite/mark”
- Typically found on glabella, eyelid or nape of neck
- Majority fade within first 2 years of life
What is a port wine stain?
- Results from low-flow vascular malfortmations of dermal capillaries
- Flat, blanching, pink-red lesions
- Present from birth
- Found anywhere on body - mostly unilateral w/ midline demarcation
- They do NOT regress + may become darker and thicker w/ age
What is a melanocytic naevi?
- Benign proliferations of subtype of melanocyte known as naevus cell
- Congenital or acquired
- Congenital → grow rapidly in infancy, start as flat lesions w/ even pigment but surface later becomes uneven, developing pebbled appearance
