Toxic Shock Syndrome

Introduction

Toxic shock syndrome (TSS) is a rapidly progressive, life-threatening illness caused not by bacterial invasion alone but by circulating bacterial exotoxins that act as superantigens, triggering an overwhelming and disproportionate immune response. It can be caused by Staphylococcus aureus (producing toxic shock syndrome toxin-1, TSST-1, or related staphylococcal enterotoxins) or by Streptococcus pyogenes (producing streptococcal pyrogenic exotoxins), and the two forms, while similar in principle, differ enough in typical presentation and severity to be worth learning separately.¹

TSS entered public awareness through its association with tampon use in the 1980s, and that history remains relevant, but the modern reality is broader: non-menstrual staphylococcal TSS and streptococcal TSS following an invasive soft tissue infection are now at least as clinically important, and streptococcal TSS in particular carries a mortality far higher than the disease's early reputation suggests.

Pathophysiology

Conventional antigens are processed and presented in a highly specific way, activating only a tiny fraction - typically less than 0.01% - of the body's T-cell population. Superantigens bypass this processing entirely: TSST-1 and the streptococcal pyrogenic exotoxins bind directly and non-specifically to the outside of MHC class II molecules on antigen-presenting cells and to the variable region of the T-cell receptor, cross-linking the two regardless of antigen specificity.

This activates up to 20-30% of the entire T-cell population simultaneously, producing a massive, indiscriminate release of pro-inflammatory cytokines - IL-1, IL-2, TNF-alpha and interferon-gamma - a "cytokine storm" that drives capillary leak, vasodilatation and profound shock, echoing the pathophysiology of sepsis but triggered by toxin rather than by the systemic spread of organisms themselves. Critically, invasive infection or even bacteraemia is not required: localised toxin-producing colonisation, for example of a retained tampon or a superficial wound, is enough to cause systemic disease.

Risk factors and precipitants

Staphylococcal TSS

• Prolonged use of high-absorbency tampons, or leaving a tampon in for an extended period (menstrual TSS)
• Other retained vaginal foreign bodies - a contraceptive diaphragm or sponge
• Nasal packing, for example after nasal surgery or for epistaxis
• Post-surgical wound infection
• Skin and soft tissue infection, including burns
• Lack of pre-existing antibody to TSST-1, which is why some people are affected and others colonised with the same organism are not

Streptococcal TSS

• Any break in skin or mucosa allowing invasive Group A Streptococcus infection - a minor wound, insect bite, or varicella lesions (a classic antecedent in children)
• Recent surgery or childbirth
• Concurrent necrotising fasciitis or other deep soft tissue infection
• Bacteraemia with Streptococcus pyogenes

Clinical features

The illness develops rapidly, often within 24-48 hours, and progresses fast. The clinical picture is built around the CDC surveillance case definitions, which remain the practical framework for recognising it.²

• Fever ≥38.9°C
• Diffuse macular erythematous rash - described as sunburn-like, involving the trunk and extremities, including the palms and soles
• Hypotension - systolic BP ≤90 mmHg in adults, or shock
• Desquamation, particularly of the palms and soles, occurring 1-2 weeks after the acute illness - a finding that confirms the diagnosis retrospectively but is never present at first presentation
• Multi-organ involvement - gastrointestinal (vomiting, profuse diarrhoea), muscular (severe myalgia with a raised creatine kinase), mucous membrane hyperaemia (conjunctival, oropharyngeal or vaginal), renal impairment, hepatic derangement, thrombocytopenia, and disorientation without focal neurology

Streptococcal TSS follows a similar pattern of fever, rash and shock, but is typically accompanied by clear, severe local signs of an invasive soft tissue infection - often necrotising fasciitis - and by a positive culture for Group A Streptococcus from blood or another normally sterile site, which is part of its formal case definition.

Differential diagnosis

• Sepsis from another source - the general approach to shock with fever applies, but TSS is distinguished by the diffuse erythema and later desquamation
• Kawasaki disease - fever, rash, mucosal changes and desquamation overlap closely, but Kawasaki disease occurs in young children and lacks the acute hypotensive shock of TSS
• Scarlet fever - a diffuse sandpaper rash from streptococcal exotoxin, but without the multi-organ dysfunction and shock of TSS
• Staphylococcal scalded skin syndrome - blistering and skin sloughing from exfoliative toxin, mainly in young children, without the same degree of shock
• Stevens-Johnson syndrome and toxic epidermal necrolysis - mucocutaneous involvement with a drug trigger, and skin sloughing rather than the delayed desquamation of TSS
• Meningococcal septicaemia - shock with a rash, but typically non-blanching and purpuric rather than diffusely erythematous

Investigations

TSS is a clinical diagnosis, made from the pattern of features above, and investigation supports it and excludes differentials rather than confirming it outright.

• FBC - thrombocytopenia is common and part of the case definition
• U&Es and creatinine - renal impairment is frequent and part of the case definition
• LFTs - hepatic derangement
• Creatine kinase - markedly raised if there is significant myositis
• Clotting screen - to look for evolving DIC in severe disease
• Blood cultures - often negative in staphylococcal TSS, since disease is toxin-mediated rather than bacteraemic; more often positive in streptococcal TSS
• Culture from the likely source - any retained tampon or foreign material, a wound swab, or a vaginal or throat swab
• Imaging if a deep or necrotising soft tissue infection is suspected, without delaying source control or surgical assessment

Management

Management mirrors that of severe sepsis and septic shock, with two additions that are specific to a toxin-mediated illness: aggressive source control, and an antibiotic regimen chosen partly for its ability to switch off toxin production.

Source control

Remove any tampon, vaginal foreign body, nasal packing or other retained material immediately. Any wound or infected focus should be actively sought, drained or debrided - if there is any suspicion of underlying necrotising fasciitis, urgent surgical review and exploration takes priority, exactly as in that condition.

Antibiotics

A combination of a beta-lactam active against Staphylococcus aureus (flucloxacillin, or vancomycin/teicoplanin if MRSA is a concern) or benzylpenicillin for confirmed streptococcal disease, together with clindamycin, is standard.

Other measures

IV immunoglobulin is used in severe or refractory cases, particularly streptococcal TSS, on the basis that pooled antibody can neutralise circulating superantigens - the evidence is strongest for streptococcal disease. Ongoing critical care support, treatment of DIC if present, and close monitoring for progression to multi-organ failure complete management.

Complications

• Multi-organ failure - renal, hepatic, respiratory and cardiovascular
• Disseminated intravascular coagulation
• Acute respiratory distress syndrome
• Digital or limb ischaemia in severe, prolonged shock, occasionally requiring amputation
• Death, particularly in streptococcal TSS
• Recurrence of staphylococcal TSS, if the patient fails to mount a protective antibody response and continues the precipitating behaviour (for example, resuming tampon use)

Prognosis

Staphylococcal TSS, treated promptly, carries a mortality of around 5%. Streptococcal TSS is substantially more dangerous, with reported mortality commonly in the range of 30-50%, reflecting its frequent association with invasive infection, bacteraemia and concurrent necrotising fasciitis. As with necrotising fasciitis, early recognition, source control and prompt antibiotics with an antitoxin agent are the factors most strongly linked to survival.