6- Dermatology (Emergency:Anaphylaxis, Erythema nodosum, Erythema multiforme, Necrotising fascitis, Steven Johnson Syndrome)) Flashcards
urticaria background
- Also known as hives
- A superficial swelling of the skin (epidermis and mucous membranes) that results in a red (initially with a pale centre), raised, and intensely itchy rash.
- Can be localised or widespread
- May be associated with angioedema and flushing
- Classification
o Acute
o Chronic
Pathophysiology of urticaria
- Causes by release of histamine and other pro-inflammatory chemicals (leukotrienes, prostaglandins) by mast cells
- Acute: allergic reaction
- Chronic: autoimmune
o Autoantibodies target mast cells
acute causes of urticaria
(mast cell release of histamine)
o Allergies to food
o Contact with chemicals, latex, nettles
o Medication
o Viral infections
o Insect bites
chronic causes of urticaria
- Chronic idiopathic urticaria: describes recurrent episodes without a clear cause
- Chronic inducible urticaria: induced by certain triggers:
o Sunlight
o Temp change
o Exercise
o Strong emotions - Autoimmune urticaria
o E.g. SLE
presentation of urticaria
- Pruritus
- Vascular permeability
- Oedema
- Rash: erythematous swelling of various shapes and sizes, classically have central pallor with erythematous flare
urticaria management
Management
- Antihistamines e.g. Fexofenadine (chronic), cetrixzine (acute)
- Oral steroids (Prednisone)may be considered for short course for severe flare
- Third line:
o Anti-leukotrienes e.g. Montelukast
o Omalizumab- target IgE
o Cyclosporin
angio-oedema vs urticaria
- Angio-oedema is a deeper form of urticaria with transient swellings of deeper dermal, subcutaneous, and submucosal tissues, often affecting the face (lips, tongue, and eyelids), genitalia, hands, or feet. For more information, see the CKS topic on Angio-oedema and anaphylaxis
- Urticaria and angio-oedema can co-exist (in about 40% of cases), but either can occur separately
- Consider vasculitis urticaria – if lesion remain for longer 24hs and are painful, non blanching and palpable (esp in conjunction with fever, malaise and arthralgia)
Patient with anaphylaxis
Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction which is likely when both of the following criteria are met:
- Sudden onset and rapid progression of symptoms.
- Life-threatening airway and/or breathing and/or circulation problems.
Classic signs of anaphylaxis
flushing, urticaria, angio-oedema
anaphylaxis aetiology
- Allergen reacts with specific IgE antibodies on mast cells and basophils (type 1 hypersensitivity reaction), triggering the rapid release of stored histamine and rapid synthesis of newly formed mediators, causing:
o Capillary leakage
o Mucosal oedema
o Shock
o Asphyxia - Usually occur over a few minutes or occasionally biphasic (may be delayed. By a few hours)
presentation of anaphylaxis
- Usually history of previous sensitivity to an allergen or recent exposure to a new drug
Skin symptoms
- Itching
- Urticaria
- Erythema
- Rhinitis
- Conjuncitivits
- Angio-oedema
Airway involvement
- Early: Itching of the palate or external auditory meatus
- Dyspnoea
- Laryngeal oedema (strodros)
- Wheezing (bronchospasm)
General symptoms
- Palpitations
- Tachycardia
- Nausea
- Vomiting
- Abdominal pain
- Faint
- Sense of impending doom
Common triggers of anaphylaxis
- Peanuts
- Eggs
- Milk
- Venom e.g. bee sting
- Drugs
o Antibiotics
o Opioids
o NSAIDs
o Contrast
o Anaesthetic
Emergency treatment
of anaphylaxis
Rapid assessment: A-E
- Give high flow oxygen (15l through a non rebreathe mask)
- Lay patient flat and raise legs
- Adrenaline IM in anterolateral aspect of the middle third of thigh
o Adult 500mg IM
o Child IM
>12 500mg
6-12- 300 mg
<6 years 150mg
o Should be repeated after 5 mins if no clinical improvement - IV fluid challenge- warmed crystalloid solution e.g. Hartmanns or saline to raise BP
- Chlorphenamine
- Hydrocortisone
- Continuing resp deterioration -> bronchodilators e.g. salbutamol
- Monitor
o Pulse oximetry
o ECG
o BP
Further investigation
- Serum mast-cell tryptase -> clarify diagnosis -> demonstrates mast-cell degranulation
Erythema nodosum
Background
- A type of panniculitis, an inflammatory disorder affecting subcutaneous fat
- Disorder where red lumps appear across the patients shins
erythema nodosum Pathophysiology
- Inflammation of subcut fat in the shins -> panniculitis
- Hypersensitivity reaction of unknown cause in most patients
erythema nodosum is more common in
women
triggers of erythema nodosum
Infection
- Streptococcal (group A beta-haemolytic)
- TB
- Gastroenteritis
Drug
- Amoxicillin
- Oral contraceptive
Chronic disease
- Sarcoidosis
- Inflammatory condition
- IBD
- Malignancy
Presentation of erythema nodosum
- Bilateral tender erythematous nodules on the anterior shins (less commonly, thighs and forearms (rarely on face)
- 3-20cm
- Lesions do not ulcerate and resolve without scarring
- Accompanied by fever and joint pain – swollen ankle most common
investigations for erythema nodosum
- Inflammatory markers (CRP and ESR)
- Throat swab for streptococcal infection
- Chest xray can help identify mycoplasma, tuberculosis, sarcoidosis and lymphoma
- Stool microscopy and culture for campylobacter and salmonella
- Faecal calprotectin for inflammatory bowel disease
management of erythema nodosum
- Treatment of underlying condition e.g. Crohn’s, sarcoidosis, tuberculosis, throat infection
- Anti-inflammatory drugs e.g. ibuprofen and hydrocortisone
- They spontaneously resolve within 6-8 weeks
presentation of erythema multiforme
- Eruption characterised by target lesion (few to hundreds within 24 hours)
- Itchy
- First seen on the back of hands/ top of feet and then spread down limb towards trunk
- Mucous membranes may be involved- stomatitis
- May have fever or chills and arthralgia -> flu symptoms
sign associated with scalded skin syndrome
Nikolsky sign is where very gentle rubbing of the skin causes it to peel away. This is positive in SSSS.
main types of nec fas
nec fas after a few hours to days
- Swelling and redness in the painful area – the swelling will usually feel firm to the touch
- Diarrhoea and vomiting
- Dark blotches on the skin that turn into fluid-filled blisters
- Subcutaenous emohysema – crepitus
Toxic epidermal necrolysis (ten) vs steven johnson (Sjs)
sjs/ten overlap and TEN form a spectrum of severe cutaneous adverse reactions (scar) that can be differentiated by the degree of skin and mucous membrane involvement.
- SJS <10% of the body
- TEN >10% of the body
skin presentation of TEN/SJS
- Lesions occur mainly on palms, soles, dorsum of hands, extensor surfaces, trunk
- Macules -> papules -> vesicles -> blue -> urticarial plaques
- Centre of the lesion may. Be vesicular, purpuric or necrotic
- Target
- Lesions become bullous and rupture
- Not pruritic - Nikolsky sign positive
- Corneal ulceration
