Diseases Flashcards
Define hypersensitivity
- immune response that causes collateral damage to self
- exaggeration of normal immune mechanisms
Describe allergy
- hypersensitivity disorder of the immune system
- allergic reactions occur when a persons immune system reacts to normally harmless substances in the environment
- a substance that causes a reaction is called an allergen
Describe a type 1 allergy
- immediate reaction; occurs within minutes and up to 2 hours after exposure to allergen
- routes of exposure; skin contact, inhalation, ingestion and injection
- history consistent with every exposure
Describe the clinical presentation of a type 1 allergy
- utricaria; very itchy, lesions appear within 1 hour, lasts 2-6 hours sometimes 24 hours, hives, wheals, nettle rash
- angioedema; localised swelling of subcutaneous tissue or mucous membranes, non pitting, not itchy
- wheezing / asthma
- anaphylaxis
Describe investigations for allergy
- history (most important)
- specific IgE (RAST)
- skin prick or prick-prick testing
- challenge test
- serum mast cell tryptase level (during anaphylaxis)
Describe skin prick / prick-prick testing
- cheap and quick
- results in 15-20 minutes
- specificity and sensitivity 90%+
- anaphylaxis risk (1:3000)
When would you do a challenge test?
Only is skin prick test was negative but history is indicative of allergy
Describe the management of allergies
- allergen avoidance
- prevent effects of mast cell activation (anti-histamines)
- anti inflammatory agent (corticosteroids)
- adrenaline autoinjector (for anaphylaxis)
- block mast cell activation (mast cell stabilisers - sodium cromogylcate)
- immunotherapy
- medic alert bracelet
- information and education
Describe adrenaline auto-injectors
- for anaphylaxis
- pre-loaded adrenaline syringe
- 300 nanograms in adults
- 150 nanograms in children
- all patients should be prescribed 2 pens
Describe non allergic reactions
- not mediated by IgE (coeliac, eosinophilic gastroenteritis)
- direct mast cell degranulation (morphine, aspirin, NSAIDs)
- metabolic (lactose intolerance)
- toxic (scombroid fish toxin)
Describe type 4 allergy
- delayed hypersensitivity
- antigen specific
- t cell mediated
- allergic contact dermatitis
- onset of reaction typically after 24-48 hours
Describe irritant contact dermatitis
- non immunological process
- contact with agents that abrade, irritate and traumatize skin directly
- does not require prior sensitisation
- pattern depends on exposure
Describe the management of irritant contact dermatitis
- allergen / irritant avoidance
- allergen / irritant minimisation
- emollients
- topical steroids
- UV phototherapy
- immunosuppressants
Dermatitis is another name for which condition?
Eczema
Describe the appearance of the acute phase of dermatitis
- papulovesicular
- erthematous (red) lesions
- oedema (spongiosis)
- ooze or scaling and crusting
Describe the appearance of the chronic phase of dermatitis
- thickening (lichenification)
- elevated plaques
- increased scaling
Names classifications of dermatitis
- contact allergic
- contact irritant
- atopic
- drug related
- photo induced or photosensitive
- lichen simplex
- stasis dermatitis
What classification of dermatitis is a delayed type / type 4 hypersensitivity reaction?
Contact allergic or drug related
Describe the immunopathology of contact allergic dermatitis
- langerhans cells in epidermis processes antigen (increased immunodeficiency)
- processed antigen is then presented to th cells in dermis
- sensitised th cells migrate into lymphatics and then to regional nodes where antigen presentation is amplified
- on subsequent antigen challenge specifically sensitised t cells proliferate and migrate to and infiltrate skin
Describe irritant (contact) dermatitis
- very common
- non specific physical irritation rather than a specific allergic reaction eg soap etc
- may be difficult to distinguish from allergic contact dermatitis
- also may overlap with atopic dermatitis
- NB types may co exist
- implications for occupation
Describe atopic eczema
- pruritus
- ill defined erythema and scaling
- generalised dry skin
- flexural distribution (varies with age)
- associated with other atopic diseases; asthma, allergic rhinitis, food allergy
Describe the chronic changes of atopic eczema
- lichenification
- excoriation
- secondary infection
What is the most common secondary infection of atopic eczema?
Staph aureus
Describe eczema herpeticum
- an infection to recognise early
- herpes simplex virus
- monomorphic punched out lesions
Describe the UK diagnostic criteria for atopic eczema
- itching plus 3 or more of;
- visible flexural rash (cheeks and extensor surfaces in infants)
- history of flexural rash
- personal history of atopy (or Fhx)
- generally dry skin
- onset before age 2 years
Describe the treatment of eczema
- plenty of emollients
- avoid irritants including shower gels and soaps
- topical steroids
- treat infection
- phototherapy; mainly UVB
- systemic immunosuppressants
- biological agents
What is the most important gene in eczema?
Filaggrin
Stasis eczema can be secondary to what?
- hydrostatic pressure
- oedema
- red cell extravasation
Define pruritus
A usually unpleasant, poorly localised, non adapting sensation that provokes the desire to scratch
What is the purpose of itch?
- lots of animal itch (possibly all mammals)
- itch always, or nearly always causes scratching
- itch is predominately a skin symptoms
- itch may be of different importance in different mammals
Describe the mediation of itch
- chemical mediators in skin; histamine, PGE2, acetylcholine, serotonin, kallikrein, interleukin 2, substance P tryptase etc
- nerve transmission; unmyelinated c fibres (different ones transmit itch and temperature from those that transmit pain)
- central nervous system mediators; opiates (endogenous and exogenous)
Name some mast cell degranulating stimuli
- allergen
- anti-fcri
- IgE
- anti-IgE
- substance P
- stem cell factor
- C5a
- codeine
Name some pre formed mediators released from mast cell degranulation
- proteases eg tryptase
- heparin
- histamine
- cytokines
Name some newly formed mediators that are synthesised for mast cell degranulation
- prostaglandin D2
- leukotrienes C4, D4, E4
- platelet activating factor
Name some causes of itch
- pruritoceptive; something (usually associated with inflammation or dryness) in skin that triggers itch
- neuropathic; damage of any sort to central or peripheral nerves causing itch
- neurogenic; no evident damage in CNS, but itch caused by eg opiate effects on CNS effectors
- psychogenic; psychological causes with no (currently detectable) CNS damage, eg itch in delusions of infestation
Name some systemic diseases associated with itch
- (mostly, not all, neurogenic itch)
- haematological
- paraneoplastic
- liver and bile duct
- psychogenic
- kidney disease
- thyroid disease
Describe the management of itch
- determine cause if possible
- treat the cause
- anti-itch treatments; sedative antihistamines, emollients, antidepressants, phototherapy, opiate antagonists
Describe the morphologies / presentation of drug eruptions
- exanthematous / morbilliform / maculopapular
- urticarial
- papulosquamous / pustular / bullous
- pigmentation
- itch pain
- photosensitivity
Describe the risk factors for drug eruptions
- age (elderly over infants)
- gender (females over males)
- genetics
- concomitant disease
- immune status
What is the most common type of drug eruption?
Exanthematous drug eruptions
Describe exanthematous drug eruptions
- most common type
- idiosyncratic, t cell mediated delayed type hypersensitivity reaction
- usually mild and self limiting
- widespread symmetrically distributed rash
- mucous membranes usually spared
- pruritus is common
- mild fever is common
- onset is 4-21 days after first taking drug
Describe indicators of a potentially severe drug eruption reaction
- involvement of mucous membrane and face
- facial erythema and oedema
- widespread confluent erythema
- fever
- skin pain
- blisters, purpura, necrosis
- lymphadenopathy, arthralgia
- shortness of breath, wheezing
Name some drugs associated with exanthematous eruptions
- penicillins
- sulphonamides
- erythromycin
- streptomycin
- allopurinol
- anti-epileptics; carbamazepine, phenytoin
- NSAIDs
- chloramphenicol
Describe urticarial drug reactions
- usually an immediate IgE mediated hypersensitivity reaction
- after rechallenge with drug
OR - direct release of inflammatory mediators from mast cells on first exposure
Describe pustular or bullous drug eruptions
- acneiform (glucocorticoids, androgens, lithium, isoniazid, phenytoin)
- acute generalised exanthematous pustulosis (rare, antibiotics, CCBs, antimalarials)
- vesicular / bullous reactions can range from mild to severe
- drug induced bullous pemphigoid
- linear IgA disease can be triggered by drugs
Describe fixed drug eruptions
- well demarcated round / oviod plaques
- red, painful
- hands, genitalia, lips, occasionally oral mucosa
- resolves with persistent pigmentation when drug stopped
- can re-occur at same site on re-exposure to drug
- usually mild when restricted to a single lesion
- can present as eczematous lesions, papules, vesicles or urticaria
Name drugs associated with fixed drug eruptions
- tetracycline, doxycycline
- paracetamol
- NSAIDs
- carbamazepine
Name some conditions associated with severe cutaneous adverse drug eruptions
- stevens johnson syndrokme (SJS)
- toxic epidermal necrolysis (TEN)
- drug reaction with eosinophilia and systemic symptoms (DRESS)
- acute generalised exanthematous pustuloss
Name some acute phototoxic drug reactions
- skin toxicity (phototoxicity)
- systemic toxicity
- photodegeneration
Name some chronic phototoxic drug reactions
- pigmentation
- photoageing
- photocarcinogenesis
Describe phototoxic cutaneous drug reactions
- non immunological skin reaction arising in an individual exposed to enough photo reactive drug and light of the appropriate wavelengths
- usually UVA / visible light
- idiosyncratic reactions can occur
- increased sensitivity to sunlight, caused by drugs, can also occur via other mechanisms eg immunosuppression or lupus
Describe patterns of skin phototoxicity
- immediate prickling with delayed erythema and pigmentation
- exaggerated sunburn
- exposed telangiectasia
- delayed 3-5 days erythema and pigmentation
- increased skin fragility
Name some drugs associated with phototoxicity
- antibiotics
- thiazides
- chlorpromazine
- NSAIDs
- quinine
- psoralens
- amiodarone
- porphyrins
- BRAF inhibitors
- antifungals
- immunosuppressants
Name common culprits of drug eruptions
- doxycycline
- chlorpromazine
- quinine
- amiodarone
Describe investigations for drug eruptions
- history and physical examination are usually sufficient to spot likely drug
- phototesting for suspected phototoxic drug eruptions
- biopsies may be useful
- patch and photopatch tests
- skin prick / intradermao tests for specific drugs
- skin testing is not indicated for serum sickness reactions or for t cell mediated reactions
Describe the management for drug eruptions
- discontinue the drug if possible
- use an alternative
- topical corticosteroids may be useful
- antihistamines may help if type 1 or with symptoms of itch
- allergy bracelets
- reported via the yellow card scheme
Define a chronic leg ulcer
An open lesion between the knee and ankle joint that remains unhealed for at least 4 weeks
Most leg ulcers are what in nature?
Venous (although often multifactorial)
Describe the assessment process of chronic leg ulcers
The main aims of assessment are to identify;
- clues to the underlying aetiology
- factors contributing to delayed healing
- SIGN assessment tool
- order of assessment is patient, leg, ulcer
When assessing an ulcer, what would be recorded?
- position of ulcer
- measure surface area
Describe vasculitis
- painful
- sudden onset
- purpuric rash / pustules
- necrotic
Describe investigations for leg ulcers
- ABPI; establish if there is arterial disease
- wound swab; only in ulcer increasingly painful, exudate, malodour or enlarging
- bloods; FBC, LFTs, U and Es, CRP
- patch testing; to previous ulcer treatments eg bandages, dressingsm creams
- duplex scan if indicated
Describe the treatment of venous ulcers
- control pain
- ABPI
- non adherent dressing
- de-sloughing agent if necessary eg hydrogel / honey
- 4 layer compression bandaging
- leg elevation
Describe the 4 layer bandaging system
- graduated compression
- 40mmHg at ankle, 25mmHg below knee
- latex / rubber free if possible
- applied by a trained nurse
- non-adherent dressing
- leg padded to a cone shape
- changed weekly, or as required
Describe wound bed preparation
- removal of devitalised tissue by debridement;
- autolytic; the use of dressings to create moist wound environment and hydrate necrotic tissue or eschar - hydrogel, honey
- sharp debridement; with scalpel or scissors
- biological; larvae therapy
- surgical; under general anaesthetic
When do we aim to heal ulcers by?
12 weeks
What is the result of vitamin D deficiency in children?
Ricketts
What is the result of vitamin deficiency in adults?
Osteomalacia
Name some indications for skin biopsy
- skin rashes; assist in diagnosis
- skin tumours; assist in diagnosis, remove malignancy, remove unwanted skin growth
Describe common melanocytic naevi
- acquired during childhood and early adulthood
- gradually lose pigment over years
- usually regular, but not always
Describe dermoscopy
- diagnostic aid, mainly used for skin lesions but use extending into hair problems / inflammatory skin disease
- recognition of morphologic structures not visible by the naked eye, thus opening up possibilities for clinical diagnosis based on dermoscopic features
Name types of skin disease due to adverse reaction to amoxicillin
- morbilliform (measles like) eruption
- urticaria
- angioedema
- fixed drug eruption
- generalised pustulosis
Describe the treatment of common precancers
- cryotherapy
- solaraze
- 5 FU
- PDT
- imiquimod
Name the five layers of the scalp
- skin
- connective tissue
- aponeurosis
- loose connective tissue
- periosteum
What is the sensory nerve supply to the face?
The trigeminal nerve
What is CN V1?
Ophthalmic division of trigeminal nerve
What is CN V2?
Maxillary division of trigeminal nerve
What is CN V3?
Mandibular division of trigeminal nerve
Describe the clinical testing of the sensory component of the trigeminal nerve
Ask the patient to close their eyes. Gently brush the skin in each dermatome with a fine tip of cotton wool. Ask the patient to tell you when they feel their skin being touched. compare the two sides
How do you test the CN VII (motor)?
Ask the patient to
- frown
- close eyes tightly
- smile
- puff out cheeks (if sphincter intact no air leaks from mouth)
Describe methods of local anaesthesia
- topical
- local infiltration
- nerve block
- field block
How can you reduce the pain during local anaesthesia?
- relax patient
- topical local
- fine needle
- warm local
- omit adrenaline
- neutralise acidity
- massage skin
- slow injection
- subcutaneous injection
- follicle opening
- nerve blocks
Describe complications of skin biopsy
- bleeding
- wound dehiscence
- infection
- scarring
- motor or sensory nerve damage
- loss of function
Describe basic skin surgery methods
- electrosurgery
- snip excision
- curettage
- shave excision
- punch biopsy
- elliptical excision
Describe electrosurgery
- variety of electrosurgery units used for
- haemostasis
- treatment of minor skin lesions eg skin tags
Describe snip excision
- grasp lesion with skin hook
- cut across base of lesion
Describe curettage and cautery
- minimally invasive procedure
- pathology specimen does not accurately record the margins of the tumour
Describe punch biopsy
- quick
- produces good wound edges but difficult to judge depth
- round holes do not always heal well
- pathology sample maybe too small
Name the five main areas of potential impact of skin disease on quality of life
- physical comfort and functioning
- acceptability to self and others
- emotional well being / self esteem
- social functioning / behavioural
- confidence in the nature and management of the condition
Describe the three types of psychosomatic skin disease
- primary skin disease precipitated or exacerbated by emotional factors
- secondary psychiatric illness arising from or exacerbated by primary skin disease
- primary psychiatric disorder which is manifest via skin lesions
Describe psychosocial variables affecting vulnerability to illness
- presence of abuse at some point in life
- life events
- grief reactions
- perception of an environment as exceeding personal resources
- interpersonal relationships providing a buffering role for stress
- psychological assets and well being
