Pathogenesis

Certain S. aureus strains (those belonging to phage group II - types 3A, 3B, 3C, 55, or 71 - but occasionally to groups I and III) cause staphylococcal scalded skin syndrome (SSSS) by releasing epidermolytic toxins.^[1] These are spread by the circulation from a localised source, causing widespread epidermal damage at distant sites. They break the epidermal cell adhesion molecule, desmoglein-1, and produce superficial skin erosion.

The same toxins that are responsible for causing SSSS also cause bullous impetigo. There appears to be a relationship between the disease extent, the amount of toxin produced and whether the toxin is released locally or systemically. As a result there is likely to be a spectrum of disease and there are likely to be a number of milder cases of adult SSSS that go undiagnosed.

Epidemiology

Social improvements and hygiene have led to a dramatic fall in the number of cases of staphylococcal scalded skin syndrome (SSSS).

SSSS typically affects neonates and children aged under 5 years, but may also occur in predisposed adults. There are now over 50 documented cases in adults and not all have an underlying illness. It may be that SSSS is less common in adults because of their higher concentrations of circulating antibodies to exfoliative toxin, and the adult kidney's ability to excrete the toxin.

In a retrospective study in England, hospital admission rates for staphylococcal septicaemia, staphylococcal pneumonia, SSSS and impetigo increased greater than 5-fold from 1989 through 2004. SSSS was seen primarily in individuals older than 16 years.^[2]

Caucasian skin is more prone to SSSS than other types and boys are twice as likely to have SSSS than girls.^[3]

Presentation

• Staphylococcal scalded skin syndrome (SSSS) usually presents with a prodrome of sore throat or conjunctivitis. The initial clinical features are fever, generalised erythema, and skin tenderness.
• Extremely tender flaccid bullae (large superficial blisters), which are Nikolsky sign-positive (where gentle shearing force on intact skin causes the upper epidermis to slip, indicating a plane of cleavage in the skin), develop within 48 hours and commonly affect the flexures; occasionally, large areas of the skin may be involved.^[4]
• The bullae enlarge and rupture easily to reveal a moist erythematous base, which gives rise to the scalded appearance.

Differential diagnosis

• For many years staphylococcal scalded skin syndrome (SSSS) and toxic epidermal necrolysis (TEN) were thought to be the same disease because of their clinical features; however, TEN is most commonly due to a drug reaction.
• The responsible toxins also cause the toxic shock syndrome but skin tenderness and Nikolsky's sign are not classic features.
• Staphylococcal scarlet fever affects mainly children of school age, and the generalised erythematous rash, classically without blisters or Nikolsky's sign, is followed on days 5-10 by desquamation.
• Blistering associated with S. aureus also occurs in bullous impetigo, in which the blisters are discrete and are not accompanied by generalised erythema.

Investigations

• Take swabs for bacteriological confirmation and antibiotic sensitivities and to identify the primary focus of infection.
• Frozen sections of the lesions can confirm the diagnosis.
• The superficial blisters are generally culture negative, but S. aureus is usually grown from material obtained from the suspected site of infection, eg umbilicus, conjunctiva, breast, surgical wound, nasopharynx or, occasionally (especially in adults), blood.^[1]
• Nasal swabs from the patient and immediate relatives should be performed to identify asymptomatic nasal carriers of S. aureus. In the case of outbreaks on wards and in nurseries, healthcare professionals should also be swabbed.

Management

It is painful and distressing for the patient and parents, although most cases respond to antibiotic treatment.

• Supportive care and appropriate attention to fluid and electrolyte management usually ensure rapid recovery.
• Moist, bare areas should be lubricated with a bland emollient to alleviate pruritus and tenderness.
• Analgesia may be required; an opioid infusion is preferred to non-steroidal anti-inflammatory drugs (NSAIDs) because the damaged skin is already prone to bleeding and renal excretion of the exotoxins makes maximised renal function important.
• Enteral nutrition must be commenced if oral intake is not possible.
• Physiotherapy is important because staphylococcal scalded skin syndrome (SSSS) tends to affect limb flexures most severely and patients will voluntarily restrict movement because of discomfort.
• Topical therapy should constitute either fusidic acid as a first-line treatment, or mupirocin in proven cases of bacterial resistance.^[5]
• First-line systemic therapy is oral or intravenous flucloxacillin.

Complications

Cellulitis, sepsis and pneumonia are possible.

Children with severe staphylococcal scalded skin syndrome (SSSS) (>50% body surface area) may need to be transferred to a tertiary paediatric burn unit for multidisciplinary care in an intensive care environment.

Prognosis

• Mortality is relatively low in infants (approximately 4%) but can be as high as 67% in adults, and depends on the extent of skin involvement and whether there are comorbidities.^[6]
• The mortality rate in children is unacceptable and outbreaks (particularly in neonatal units) can be difficult to control.