18.1 | Introduction |
- Rashes that kill: there are several rashes which must be diagnosed because early treatment may be lifesaving. The spreading urticaria and erythema that may suggest anaphylaxis along with wheeze, hypotension. The non-blanching purpuric rash of meningococcaemia with possible meningitis. The rapidly advancing all consuming, painful, red, hot necrotising fasciitis which spreads in hours. The slower advancing red, hot, tender cellulitis or erysipelas which can result in systemic sepsis.
- Other life threatening rashes include pemphigus vulgaris, toxic epidermal necrolysis (milder form called Stevens–Johnson syndrome (SJS)), erythema multiforme major, drug rash with eosinophilia and systemic symptoms (DRESS) syndrome, toxic shock syndrome (TSS).
18.2 | Toxic epidermal necrolysis/Stevens–Johnson syndrome |
- About: involves skin as well as mucous membranes – mouth, genitals, vagina, eyes. TEN is a more severe form of SJS. Ask about drugs within the preceding 2 months as a reaction may be delayed.
- Aetiology: idiopathic – worse prognosis than drug-induced. Drug-induced – sulphonamides, cephalosporins, antibiotics, anticonvulsants. Commoner with HIV and in slow drug acetylators.
- Clinical: preceding flu-like illness with myalgia, fever in recent days. Milder: erythema, target lesions, blistering on skin and oral/genital mucosa. Spreading tender erythema and confluent blistering rash followed by loss of sheets of epidermis. Pain may be severe. Involves skin and oral/genital mucosa. Detachment of the skin and mucosal epidermis. Progressive exfoliation. Recovery may lead to scarring, altered pigmentation and loss of sweating. Positive Nikolsky sign when slight lateral pressure to the epidermal surface slips upper layers away from lower.
- Differential: staphylococcal scalded skin syndrome (seen in children and mucosa spared). Toxic shock syndrome, phototoxic skin reactions. Drug reaction with eosinophilia.
Prognostic severity factors for toxic epidermal necrolysis
- Age >40 years +1, HR >120 +1, cancer or haematological malignancy +1.
- Involved body surface area >10% +1, urea >10 mmol/L +1, HCO–3 <20 mmol/L +1.
- Blood glucose level >14 mmol/L +1.
- Mortality rates: 0–1 = 3%, 2 = 12%, 3 = 35%, 4 = 58%, 5 or more = 90%.
- Investigation: bloods: FBC, U&Es, LFT, CRP. Blood cultures, urine culture, CXR if febrile. Skin biopsy: necrotic keratinocytes with full thickness epithelial necrosis and sheets of epidermal detachment helps differentiate from staphylococcal scalded skin syndrome.
- Management (urgently speak with dermatologist): stop all possible drug causes, early detection. Optimise hydration. Watch input/output. Low threshold for starting antibiotics or antivirals for any superinfection. Transfer to burns unit. Supportive – fluid balance and nutrition, avoid hypothermia. Some may consider IVIG but steroids/immune suppression not indicated. Appropriate bedding – Clinitron mattress, avoid IV lines to reduce sepsis. Fluid/nutrition orally or via NG tube. Eye care to avoid scarring. VTE prophylaxis.
18.3 | Cellulitis/erysipelas, bites, surgery |
- About: beware over-treating chronic bilateral usually cold or warm mildly tender red legs. It’s possible, but unusual, for cellulitis to be symmetrical. It may be chronic changes. Always look and feel all cases yourself. Unwrap bandages. Look at CRP, etc. Distal skin integrity key and simple emollients can soften dry eczematous legs.
- Organism: cellulitis mostly due to β-haemolytic streptococci. Often initially slow to respond to therapy or may worsen initially due to toxins produced by group A strep. and other local tissue factors. Less common Staph. aureus and MRSA.
- Clinical: subcutaneous skin infection. Red, very painful swelling often of a limb. Pyrexia and malaise. Inguinal nodes. Look for the point of entry – dry cracked skin between toes or insect bite or trauma. Look at heels and back of legs.
- Diagnosis:
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