Erythrodermic Psoriasis

Erythrodermic psoriasis is a severe form of psoriasis with confluent erythema over at least 90% of the body surface, with scaling and systemic disturbance. It is a dermatological emergency because of thermoregulatory failure, fluid and protein loss and high output cardiac failure.

It occurs in about 1 to 2% of people with psoriasis, mostly adults, and may be the first presentation or follow long standing plaque disease. Mortality is raised, from sepsis, heart failure and metabolic disturbance.

Triggers include withdrawal of systemic corticosteroids or immunosuppressants, infection, HIV, sunburn, severe stress, drugs (lithium, antimalarials, beta blockers), alcohol and irritant topical treatment such as tar or dithranol at high concentration. Some cases are idiopathic.

Pathophysiology.

Widespread activation of the interleukin-23 and interleukin-17 axis causes uncontrolled keratinocyte proliferation and cytokine release. Peripheral vasodilatation leads to heat loss, high cardiac output and raised insensible water loss. Protein and iron are lost in scale and through the skin.

• Generalised erythema and fine or exfoliative scale, with warmth and itch or burning.
• Fever or hypothermia, chills, malaise, tachycardia and peripheral oedema.
• Nail dystrophy, hair loss, ectropion and lymphadenopathy.
• Complications: dehydration, electrolyte disturbance, hypoalbuminaemia, high output cardiac failure, sepsis, kidney injury and thromboembolism.

Red flags.

• Hypotension, tachycardia over 120 beats/min, temperature instability or confusion.
• Pustules, suggesting generalised pustular psoriasis.
• Drug history of recent steroid withdrawal.

• Clinical diagnosis, with a history of psoriasis, and exclusion of other causes of erythroderma.
• Full blood count, urea and electrolytes, creatinine, albumin, liver tests, calcium, C-reactive protein, uric acid, glucose, thyroid function and HIV test.
• Skin biopsy (psoriasiform dermatitis with parakeratosis), and blood film with immunophenotyping when cutaneous T-cell lymphoma with circulating atypical cells is possible.
• Cultures, ECG and echocardiography if infection or cardiac failure is suspected.
• Drug history, and patch testing when contact dermatitis is possible.

Differential diagnosis. Atopic dermatitis, drug eruption including DRESS, cutaneous T-cell lymphoma, pityriasis rubra pilaris, contact dermatitis, pemphigus foliaceus, generalised ichthyosis and HIV-associated erythroderma.

Supportive care.

• Admit to a warm room with monitoring of temperature, pulse, blood pressure, urine output, daily weight and electrolytes.
• Fluid and electrolyte replacement, nutritional support with high protein intake, thromboprophylaxis, and treatment of infection.
• Bland emollients applied frequently, with wet wraps, bathing and mild topical corticosteroids (hydrocortisone 1% or clobetasone butyrate 0.05%). Avoid irritant tar and dithranol.
• Avoid systemic corticosteroids because of rebound pustulation and erythroderma.

Systemic treatment.

• Rapid control: ciclosporin 2.5 to 5 mg/kg/day in two divided doses, or infliximab 5 mg/kg intravenously at weeks 0, 2 and 6, then every 8 weeks.
• Maintenance: acitretin 25 to 50 mg daily, or methotrexate 7.5 to 25 mg once weekly with folic acid 5 mg weekly. Do not exceed 1 year of continuous ciclosporin without review.
• Biologics: secukinumab 300 mg at weeks 0, 1, 2, 3 and 4 then every 4 weeks, ixekizumab, ustekinumab 45 mg (90 mg if over 100 kg) at weeks 0 and 4 then every 12 weeks, or risankizumab 150 mg at weeks 0 and 4 then every 12 weeks. Screen for tuberculosis, hepatitis B, hepatitis C and HIV before starting.

Monitoring. Daily vital signs and fluid balance during admission, then review every 1 to 2 weeks until stable. Monitor ciclosporin blood pressure and creatinine, methotrexate full blood count and liver tests, and acitretin lipids and liver tests.

Referral and escalation. Refer urgently to dermatology, with intensive care for hypotension, high output cardiac failure or sepsis.

Special groups. Pregnancy: ciclosporin or certolizumab with specialist input, and avoid methotrexate and acitretin. In older patients take care with fluid loading because of cardiac failure.