Steven Johnson Syndrome / Toxic Epidermal Necrolysis Flashcards

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1
Q

What is Stevens-Johnson syndrome and Toxic epidermal necrolysis (TEN)?

A

Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) => variants of the same condition.

SJS/TEN is a rare, acute and potentially fatal skin reaction with sheet-like skin and mucosal loss.
=> nearly always caused by medications.

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2
Q

Who is at risk of SJS/TEN?

What genetics factors increase the risk?

Which drugs increase the risk?

What is the most common drug assoc. with SJS/TEN?

A
  1. Anyone on medication can develop SJS/TEN unpredictably
  2. Females > Males (only v slightly)
  3. 100x more common in HIV
  4. Genetic factors:
    => HLA associations in some races to anticonvulsants and allopurinol

=> Polymorphisms e.g. CYP2C coding for cytochrome P450 in patients reacting to anticonvulsants

  1. > 200 medications associated with SJS/TEN
  2. Most common drugs that cause SJS/TEN = antibiotics
  3. Other drugs include:
    => Sulfonamides: cotrimoxazole

=> Beta-lactam: penicillins, cephalosporins

=> Anti-convulsants: lamotrigine, carbamazepine, phenytoin, phenobarbitone

=> Allopurinol

=> Paracetamol/acetaminophen

=> NSAIDs

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3
Q

What are the clinical features of SJS/TEN?

A

Usually develops within the first week of antibiotic therapy but up to 2 months after starting an anticonvulsant.

Prodromal illness: non-specific, flu-like illness. Symptoms include:
=> Fever > 39 C
=> Sore throat, difficulty swallowing
=> Runny nose and cough
=> Sore red eyes, conjunctivitis
=> General aches and pains.

Followed by an abrupt onset of a tender/painful red skin rash starting on the trunk and extending rapidly over hours to days onto the face and limbs
=> rarely affects scalp, palms or soles

The skin lesions may be:

=> Macules — flat, red and diffuse (measles-like spots) or purple (purpuric) spots

=> Diffuse erythema
=> Erythema multiforme
=> Flaccid blisters (TENS)

The blisters merge to form sheets of skin detachment, exposing red, oozing dermis.

Nikolsky sign +ve in areas of skin redness.
=> meaning blisters and erosions appear when skin is rubbed gently

Mucosal involvement is prominent and severe. At least 2 mucosal surfaces are affected including:

=> Eyes (conjunctivitis, less often corneal ulceration, anterior uveitis) — red, sore, sticky, photosensitive eyes

=> Lips/mouth (cheilitis, stomatitis) — red crusted lips, painful mouth ulcers

=> Pharynx, oesophagus - difficulty eating

=> Genital area and urinary tract - erosions, ulcers, urinary retention

=> Upper respiratory tract (trachea and bronchi) - cough & respiratory distress

=> Gastrointestinal tract -diarrhoea

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4
Q

What are the complications of SJS/TEN?

A

Fatal => complications in the acute phase
=> mortality rate = 10% for SJS and 30% for TEN

During the acute phase, potentially fatal complications include:

=> Dehydration and acute malnutrition

=> Infection of skin, mucous membranes, lungs (pneumonia), septicaemia (blood poisoning)

=> Acute respiratory distress syndrome

=> Gastrointestinal ulceration, perforation and intussusception

=> Shock and multiple organ failure including kidney failure

=> Thromboembolism and disseminated intravascular coagulopathy

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5
Q

How is SJS/TEN diagnosed?

A

SJS/TEN = clinical diagnosis and classified based on the skin surface area detached

  1. Stevens-Johnson Syndrome
    => Skin detachment <10% of body surface area
    => Widespread erythematous or purpuric macules
  2. Overlap SJS/TEN
    => Detachment between 10% and 30% of body surface area
    => Widespread purpuric macules or flat atypical targets
  3. TEN with spots
    => Detachment >30% of body surface area
    => Widespread purpuric macules or flat atypical targets
  4. TEN without spots
    => Detachment of >10% of body surface area
    => Large epidermal sheets and no purpuric macules
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6
Q

What investigations are carried out in SJS/TEN?

A

Raised serum Granulysin in the first few days of drug eruption = predictive of SJS/TEN

Skin biopsy
=> confirms clinical diagnosis
=> excludes staphylococcal scalded skin syndrome (SSSS) + other generalised rashes with blisters

Histopathology:
=> keratinocyte necrosis (death of skin cells)

=> full thickness epidermal/epithelial necrosis (death of an entire layer of skin)

=> minimal inflammation (very mild lymphocytic infiltrate of the superficial dermis)

=> Direct immunofluorescence test on skin biopsy = negative, indicating disease is not due to deposition of antibodies in the skin.

Blood tests
=> essential for fluid and nutrients replacement

i. Anaemia
ii. Leucopenia + lymphopenia (90%)
iii. Neutropenia (bad prognostic sign)
iv. LFT: Mildly raised liver enzymes + 10% develop overt hepatitis
v. Mild proteinuria (50%)

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7
Q

What is SCORTEN?

A

SCORTEN = illness severity score to predict mortality in SJS and TEN cases.

One point is scored for each of the seven criteria present at the time of admission.

Age >40 years

Presence of malignancy (cancer)

Heart rate >120

Initial percentage of epidermal detachment >10%

Serum urea level >10 mmol/L

Serum glucose level >14 mmol/L

Serum bicarbonate level <20 mmol/L

The risk of dying from SJS/TEN depends on the score
SCORTEN 0-1 = >3.2%
SCORTEN 2  = >12.1%
SCORTEN 3 = >35.3%
SCORTEN 4 = >58.3%
SCORTEN 5 or more = >90%

*In 2019, a new prediction model was proposed, the ABCD-10.

A: age over 50years (1pts)

B: bicarbonate level <20 mmol/L (1pts)

C: cancer present and active (2pts)

D: dialysis prior to admission (3pts)

10: epidermal detachment ≥ 10% body surface area on admission (1pts)

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8
Q

What are the differential diagnosis for SJS/TEN?

A

Other severe cutaneous adverse reactions (SCARs) to drugs e.g. drug hypersensitivity syndrome

Staphylococcal scalded skin syndrome and toxic shock syndrome

Erythema multiforme

Mycoplasma infections

Bullous systemic lupus erythematosus

Paraneoplastic pemphigus

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9
Q

What is the treatment for SJS/TEN?

A

Cessation of causative drug

Manage in dermatology / burns unit

Short term dexamethasone pulse therapy

Nutrition + fluid (crystalloid) replacement IV

Temperature maintenance

Pain relief

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