Dermatology

Question 1

A 35-year-old woman presents to the emergency department with a painful rash, starting on her trunk and spreading to her face and limbs. She recently started taking carbamazepine for epilepsy. Possible diagnosis?

Answer 1

Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis

Question 2

What are Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis?

Answer 2

Stevens-Johnson syndrome (SJS) + toxic epidermal necrolysis (TEN) = severe systemic cutaneous adverse reactions → characterised by epidermal necrosis + detachment.

These reactions are thought to be immunologically mediated - often triggered by medications → involve apoptosis of keratinocytes

The disease is classified by the extent of body surface area involved:
* SJS: <10%
* SJS/TEN overlap: 10-30%
* TEN: >30%

Question 3

Risk factors for Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Answer 3

• Medications (sulfa drugs, penicillins, cephalosporins, antiepileptics (lamotrigine, carbamazepine, phenytoin), allopurinol, NSAIDs, the oral contraceptive pill)
• Infections (e.g. Mycoplasma pneumoniae, HIV)
• Sex: Female

Question 4

Clinical features of Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Answer 4

Signs:
* Nikolsky sign: when lateral pressure is applied - the epidermis separates → results in blistering + erosions
* Erythematous or purpuric macules, rapidly evolving into widespread blistering and desquamation
* Mucosal involvement
* Pyrexia
* Tachycardia

Symptoms:
* Fever, malaise: typically prodromal
* Sore throat + eyes

Question 5

Investigations for Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Answer 5

• Skin biopsy = confirms diagnosis (showing full-thickness epidermal keratinocyte necrosis + minimal dermal inflammation
• Serum granulysin (elevated levels, measured within the first few days of the drug eruption)

Investigations to consider:
* FBC, CRP and blood cultures: to exclude staphylococcal scalded skin syndrome. Also investigate secondary infecton + sepsis
* U&E: look for dehydration + pre-renal acute kidney injury

Question 6

What scores are used to predict mortality in patients with SJS and TEN?

Answer 6

ABCD 10 + SCORTEN

Question 7

Management of Stevens-Johnson Syndrome and Toxin Epidermal Necrolysis

Answer 7

First-line:
* Withdrawal of causative drug
* Hospital admission
* Supportive care: fluid + electrolyte management, temperature regulation, wound care and nutritional support , ideally in an intensive care or burns unit with specialist nursing care
* Analgesia
* Eye care: daily ophthalmology review
* Mouth care
* ** IV immunoglobulin**

Second-line:
* Immunosuppressants (e.g. ciclosporin or cyclophosphamide)
* Systemic corticosteroids
* Plasmapheresis

Question 8

Complications of SJS and TEN

Answer 8

• Secondary infection leading to sepsis
• Dehydration
• Electrolyte derangement
• Renal failure
• Acute respiratory distress syndrome
• Thromboembolism and disseminated intravascular coagulopathy
• Skin scarring (hypo- or hyper-pigmentation)
• Ocular complications: e.g. ulceration