Emergency dermatology Flashcards
List some causes of urticaria, angioedema and anaphylaxis
Idiopathic Food Drugs Insect bites Contact - latex Viral infection Parasitic infection Autoimmune Hereditary
Describe the pathophysiology of urticaria
Due to a local increase in permeability of capillaries and small venules. Large number of inflammatory mediators (prostaglandins, leukotrienes and chemotactic factors) play a role but histamine derived from skin mast cells appears to be major mediator
Local mediator release from mast cells can be induced by immunological and non-immunological mechanisms
How does urticaria present
Swelling involving the superficial dermis, raising the epidermis - itchy wheals
How does angioedema present?
Deeper swelling involving the dermis and subcutaneous tissue - swelling of the tongue and lips
How does anaphylaxis present?
Bronchospasm
Facial and laryngeal oedema
Hypotension
Can initially present with urticaria and angioedema
What is the management of urticaria?
Antihistamines
What is the management of angioedema?
Corticosteroids
What is the management of anaphylaxis?
Adrenaline
Corticosteroids
Antihistamines
What is a complication of angioedema and anaphylaxis
Asphyxiation and death
What is erythema nodosum
A hypersensitivity response to a variety of stimuli
What causes erythema nodosum
Group A beta haemolytic streptococcus Primary tuberculosis Pregnancy Malignancy IBD Chlamydia Leprosy
How does erythema nodosum present
Discrete tender nodules which may become confluent
Usually appear on the shins
As they resolve they become bruise like in colouration
Lesions continue to appear for 1-2 weeks
Lesions do not ulcerate and resolve without atrophy or scarring
Describe erythema multiforme
Often of unknown cause - herpes simplex virus may precipitate it
Self limiting acute inflammatory condition
Mucosal involvement is absent/limited to one mucosal surface only
Describe Steven Johnson syndrome
Characterised by mucocutaneous necrosis with at least 2 mucosal sites involved
Skin involvement may be limited or extensive
Drugs or combinations of infections or drugs may be associated
Epithelial necrosis with few inflammatory cells seen on histopathology.
May have a prodromal illness
Describe toxic epidermal necrosis
Usually drug induced
Acute severe disease characterised by extensive skin and mucosal necrosis accompanied by systemic toxicity
Describe the management of TEN and SJS
Early recognition and call for help
Full supportive care to maintain haemodynamic equilibrium
What is the mortality rate for SJS
12%
What is the mortality rare for TEN
> 30%
What is death from SJS and TEN usually due to?
Sepsis, electrolyte abnormalities or multiorgan failure
Describe acute meningococcaemia
A serious communicable infection transmitted via respiratory secretions, bacteria get into the circulating blood
What organisms cause acute meningococcaemia
Gram negative diplococcus Neisseria meningitides
Describe the presentation of acute meningococcaemia
Features of meningitis - headache, fever, neck stiffness
Features of septicaemia - Hypotension, fever, myalgia
Typical rash - non blanching purpuric rash on trunk and extremities which may be preceded by a maculopapular rash and can rapidly progress into ecchymoses, haemorrhagic bullae and tissue necrosis
What is the treatment of acute meningococcaemia
Antibiotics (eg. benzylpenicillin) Prophylactic antibiotics (eg. rifampicin) for close contacts (ideally within 14 days of exposure)
What are the complications of acute meningococcaemia
DIC
Septic shock
Multiorgan failure
Death
What is erythroderma
Exfoliative dermatitis involving at least 90% of the skin surface
List some causes of erythroderma
Previous skin disease - eczema and psoriasis
Lymphoma
Drugs - sulphonamides, gold, sulphonlyureas, penicillin, allopurinol, captopril
Idiopathic
How does erythroderma present?
Skin appears inflamed, oedematous and scaly
Systemically unwell with malaise and lymphadenopathy
How is erythroderma treated?
Treat the underlying cause
Emollients and wet wraps
Topical steroids to reduce inflammation
What are the complications of erythroderma
Secondary infection Fluid loss Electrolyte imbalance Hypothermia High output cardiac failure Capillary leak syndrome
Describe the prognosis for erythroderma
Depends on underlying diagnosis - 20-40%
Describe eczema herpeticum
Widespread eruption - serious complication of eczema
What causes eczema herpeticum
Herpes simplex virus
Describe the presentation of eczema herpeticum
Extensive crusted papules, blisters and erosions
Systemically unwell with fever and malaise
Describe the management of eczema herpeticum
Antivirals
Antibiotics for any secondary bacterial infection
List the complications of eczema herpeticum
Herpes hepatitis
Encephalitis
DIC
Rarely death
Describe necrotising fasciitis
A rapidly spreading infection of the deep fascia with secondary tissue necrosis
What causes necrotising fasciitis
Group A haemolytic streptococci
Mixture of anaerobic and aerobic bacteria
What are the risk factors for necrotising fasciitis
Abdominal surgery
Medical comorbidity - diabetes and malignancy
Although 50% occur in healthy individuals
Describe the presentation of necrotising fasciitis
Severe pain
Erythematous, blistering and necrotic skin
Systemically unwell with fever and tachycardia
Presence of crepitus - subcutaneous emphysema
What may an x-ray show in necrotising fasciitis
Soft tissue gas
How is necrotising fasciitis managed
Urgent referral for surgical debridement
IV antibiotics
What is the prognosis of necrotising fasciitis
Mortality up to 76%
