Dermatology - Emergency dermatology Flashcards
What causes urtiacaria, angioedema and anaphylaxis?
Idiopathic Food (e.g. nuts, shellfish, dairy) Drugs (e.g. penicillins, NSAIDs, contrast media, morphine, ACEi) Insect bites Contact (e.g. latex) Viral or parasitic infections Autoimmune Hereditary (some cases of angioedema)
What is the pathogenesis of urticaria?
Urticaria is due to local increase in permeability of capillaries and small venules. A large number of inflammatory mediators play a role, but histamine derived from mast cells is the major mediator. Local mediator release can be immunological or non immunologically induced.
How does urticaria present?
Urticaria (swelling of superficial dermis, raising the epidermis) presents with itchy wheals.
How does angioedema present?
Angioedema (deeper swelling involving the dermis and subcutaneous tissue) presents with swelling of the lip and tongue.
How does anaphylaxis present?
Bronchospasm, facial and laryngeal oedema, hypotension; can present initially with angioedema and urticaria.
How is angioedema, urticaria and anaphylaxis managed?
Antihistamines for urticaria.
Corticosteroids for severe acute urticaria and angioedema.
Adrenaline (1:1000), corticosteroids and antihistamines for anaphylaxis.
What is erythema nodosum?
A hypersensitivity response to a variety of stimuli.
Causes include:
- Group A beta haemolytic strep
- Primary TB
- Malignancy
- Sarcoidosis
- IBD
- Chlamydia
- Leprosy
How does erythema nodosum present?
Discrete tender nodules which may become confluent.
Lesions continue to appear for 1-2 weeks and leave a bruise like discolouration when they resolve. But they do not ulcerate and resolve without scarring. Shins are the most common site.
What is erythema multiforme?
The aetiology is often unknown, but it is an acute self limiting inflammatory condition with herpes simplex virus being the main precipitating factor. Other infections and drugs can be involved*. Mucosal involvement is usually absent or limited to one surface only.
*Other causes include malignancy, sarcoidosis, and drugs (penicillins, sulphonamides etc).
How does erythema multiforme present?
“Target lesions” - initially on the back of the hands/ feet before spreading to the torso. Upper limbs are more commonly affected than lower limbs. Pruritis is occasionally seen and is usually mild.
What is Stevens-Johnson syndrome?
Stevens-Johnson syndrome is a severe form of erythema multiforme associated with mucosal involvement and systemic symptoms. It is characterised with mucocutaneous necrosis with at least 2 mucosal sites involved. Drugs or combinations of drugs and infections is the main cause. Stevens-Johnson syndrome may have features overlapping with toxic epidermal necrolysis including a prodromal illness. Systemic features include fever and arthralgia.
What is toxic epidermal necrolysis?
TEN is a potentially life threatening skin disorder that is most commonly seen secondary to a drug reaction. In this condition the skin develops a scalded appearance over an extensive area. Some authors consider TEN to be the severe end of a spectrum of skin disorders which includes erythema multiforme and Stevens-Johnson syndrome.
Features:
- systemically unwell e.g. pyrexia, tachycardic
- positive Nikolsky’s sign: the epidermis separates with mild lateral pressure
What drugs are known to cause TEN?
phenytoin sulphonamides allopurinol penicillins carbamazepine NSAIDs
How is TEN managed?
stop precipitating factor
supportive care, often in intensive care unit
intravenous immunoglobulin has been shown to be effective and is now commonly used first-line
other treatment options include: immunosuppressive agents (ciclosporin and cyclophosphamide), plasmapheresis
What is acute meningococcaemia?
A serious communicable infection transmitted via respiratory secretions; bacteria get into circulating blood. It is caused by the gram negative diplococcus Neisseria meningitides.
