Staphylococcal scalded skin syndrome: SAQ

Short-answer questions on a febrile infant with rapidly spreading tender erythema and sheet-like desquamation, covering recognition of staphylococcal scalded skin syndrome, the desmoglein 1 mechanism, the distinction from Stevens-Johnson syndrome, and anti-staphylococcal antibiotic selection.

Prompt

A previously well 14-month-old boy is brought to the emergency department with two days of irritability and low-grade fever. This morning his mother noticed redness around his mouth and in the folds of his neck and axillae, and over the last few hours his skin has begun to peel off in sheets when she dresses him. On examination he is fretful and febrile at 38.4 degrees C, with widespread scarlet erythema, flaccid bullae, and large areas of moist raw skin across his trunk and flexures. His mouth, eyes, and genital mucosa are intact. The surrounding skin shears off when lightly stroked.

This infant presents the classic constellation of generalised staphylococcal scalded skin syndrome: a prodrome of irritability and fever, scarlet erythema around the mouth and flexures, flaccid bullae, and sheet-like peeling with a positive Nikolsky sign. The sparing of the oral, conjunctival, and genital mucosae is the single feature that separates this from Stevens-Johnson syndrome and toxic epidermal necrolysis, and it should be documented explicitly. This is a toxin-mediated disease in which the source is remote, the skin heals without scarring, and anti-staphylococcal antibiotics switch off the toxin. ^[2]

Question 1 (10 marks)

Outline the pathophysiology of this condition, and explain why the mucous membranes are spared. ^[1]

The disease is produced by phage-group-II Staphylococcus aureus that colonises a distant focus such as the conjunctiva, the umbilicus, the nasopharynx, or the nappy area. The organism secretes exfoliative toxin A, which is chromosomally encoded and heat-stable, and exfoliative toxin B, which is plasmid-encoded and heat-labile. These toxins are serine proteases with a precise specificity for desmoglein 1, the desmosomal adhesion molecule that binds superficial keratinocytes. ^[1]

The toxin travels in the blood to the skin, where it cleaves desmoglein 1 in the stratum granulosum, dissolving the glue between the outermost keratinocytes. The split is therefore superficial, which is why the skin peels like a scald but heals without scarring, and why the Nikolsky sign is positive. Infants clear the toxin slowly through immature kidneys, which is why the disease is overwhelmingly one of the very young. ^[2]

The mucous membranes are spared because desmoglein 3, which the toxin does not cleave, takes over the adhesion role in the oral, conjunctival, and genital surfaces. This single molecular fact is the cardinal clue against Stevens-Johnson syndrome and toxic epidermal necrolysis, in which the mucosae are involved and the split is full-thickness. Documenting the intact mucosae at every assessment keeps this distinction clear. ^[2]

References3Show

[1]Ladhani S Clinical, microbial, and biochemical aspects of the exfoliative toxins causing staphylococcal scalded-skin syndrome. Clin Microbiol Rev, 1999.PMID 10194458
[2]Ladhani S Staphylococcal scalded skin syndrome. Arch Dis Child, 1998.PMID 9534685
[3]Handler MZ Staphylococcal scalded skin syndrome: diagnosis and management in children and adults. J Eur Acad Dermatol Venereol, 2014.PMID 24841497

Staphylococcal scalded skin syndrome: SAQ

Question 1 (10 marks)

Outline the pathophysiology of this condition, and explain why the mucous membranes are spared. ^[1]

References3Show

[1]Ladhani S Clinical, microbial, and biochemical aspects of the exfoliative toxins causing staphylococcal scalded-skin syndrome. Clin Microbiol Rev, 1999.PMID 10194458
[2]Ladhani S Staphylococcal scalded skin syndrome. Arch Dis Child, 1998.PMID 9534685
[3]Handler MZ Staphylococcal scalded skin syndrome: diagnosis and management in children and adults. J Eur Acad Dermatol Venereol, 2014.PMID 24841497