Pustular and erythrodermic psoriasis

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Unstable psoriasis is a medical as well as dermatological emergency. The immediate problem is loss of barrier physiology and systemic inflammation; identifying the exact subtype proceeds alongside stabilisation, not before it.

Pustules in generalised pustular psoriasis are sterile, but secondary infection is common and sepsis may look similar. Erythroderma is a final common appearance with several causes, so established psoriasis never removes the need for medicine review and differential diagnosis.

Safe management has three parallel tracks: supportive organ care, removal of an evidenced precipitant without hazardous abrupt withdrawal, and specialist anti-inflammatory treatment with close laboratory and clinical monitoring.

Key points

Generalised pustular psoriasis causes widespread tender erythema studded with superficial sterile pustules; erythroderma means near-generalised inflammation and scale with systemic barrier failure.
NICE requires immediate same-day specialist assessment and treatment for generalised pustular psoriasis or erythroderma.
Perform ABCDE, full observations, core temperature, fluid balance and urine output; assess sepsis, cardiac strain and venous thromboembolism risk in parallel.
Take a dated timeline of psoriasis therapies, systemic corticosteroid exposure, new medicines, infection, pregnancy and adherence; do not abruptly stop an effective systemic agent without specialist direction.
Skin pain, mucosal erosions, dusky targets, blisters or detachment should redirect urgently toward severe drug reaction rather than being absorbed into a psoriasis label.
Initial tests include blood count, inflammatory markers, renal and liver profile, calcium, magnesium, albumin, cultures when infection is possible, and pregnancy testing where relevant to treatment.
Provide gentle emollient skin care, non-adhesive dressings, warmth and carefully monitored replacement while specialist therapy is selected; avoid irritant topicals over vast inflamed areas.
Systemic choice is consultant-led: NICE supports ciclosporin when rapid control is needed and acitretin for pustular forms, with phenotype, comorbidity, pregnancy potential and organ function governing selection.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Psoriatic instability

Generalised pustular psoriasis and erythrodermic psoriasis are uncommon severe phenotypes driven by intense inflammation. They may occur in known psoriasis or be the first recognised presentation.

Triggers and withdrawals

Infection, pregnancy, hypocalcaemia, medicine exposure and abrupt withdrawal of systemic corticosteroid or other effective psoriasis treatment can precipitate instability. A dated prescription and adherence history is essential.

Non-psoriatic erythroderma

Eczema, drug reactions, cutaneous T-cell lymphoma, pityriasis rubra pilaris and other inflammatory disorders can produce erythroderma. Previous psoriasis raises probability but does not settle causation.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Neutrophilic pustulation
Cytokine-driven neutrophil recruitment creates superficial sterile pustules that may coalesce into lakes of pus. Sterility is a pathological concept; clinically unwell patients still need cultures and sepsis assessment.
2
Barrier failure
Extensive inflamed skin loses water, electrolytes, protein and heat control while allowing microbial entry. Oedema and hypoalbuminaemia can coexist with intravascular depletion.
3
Systemic inflammatory load
Cutaneous inflammation drives vasodilatation, tachycardia and increased metabolic demand. Older people and those with cardiac or renal disease may decompensate before surface appearance seems dramatic.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Generalised sterile pustulesRed flag

Sheets of small superficial non-follicular pustules develop on hot tender inflamed skin and may merge. Pustule contents are not assumed infectious, but fever and neutrophilia cannot distinguish sterile inflammation from sepsis.

Erythrodermic inflammationRed flag

Most of the skin becomes inflamed, warm and scaly, sometimes obscuring original plaque borders. In deeply pigmented skin, widespread darkening, violaceous change and heat may be more apparent than redness.

Barrier failureRed flag

Shivering, oedema, thirst, oliguria, hypotension, confusion or temperature abnormality indicates physiologic loss through diseased skin. Record weight and input-output as well as the rash extent.

Drug-reaction cluesRed flag

New medicine exposure, facial oedema, mucosal disease, targetoid or dusky lesions, skin pain, blistering, eosinophilia or internal-organ injury makes a severe cutaneous adverse reaction more likely.

Focal infection clueRed flag

Asymmetric rapidly advancing warmth, focal purulence, crepitus, marked tenderness or haemodynamic sepsis warrants immediate infection and surgical pathways; inflammatory psoriasis does not protect against invasive infection.

Palmoplantar limitation

Recurrent sterile pustules confined to palms and soles without systemic upset are palmoplantar pustulosis, a chronic high-impact condition, not the same emergency as disseminated generalised pustular psoriasis.

Red flags requiring action

Fever, tachycardia, hypotension, reduced urine output, confusion, shivering, oedema or breathlessness indicates physiological compromise and requires emergency assessment.
Skin pain, dusky areas, blisters, epidermal detachment, mucosal erosions or a recent high-risk medicine suggests severe cutaneous adverse reaction rather than assuming psoriasis.
Purpura, rapidly spreading warmth, focal fluctuance, positive sepsis features or disproportionate pain raises concern for invasive infection requiring immediate antimicrobial and surgical assessment.
Pregnancy with generalised pustulation is a specialist emergency because maternal electrolyte disturbance and placental or fetal complications may occur.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line physiological assessmentFirst stepFirst line
Why
Detect shock, respiratory compromise, temperature disturbance, acute kidney injury and fluid loss immediately.
Interpretation and limitations
Trend heart rate, blood pressure, oxygen saturation, core temperature, mental state, urine output and weight; normal values at one time point do not exclude subsequent deterioration.
02
Blood count, CRP, renal profile, liver profile, calcium, magnesium and albumin
Why
Measure systemic inflammation, organ injury, electrolyte loss and protein depletion before systemic treatment.
Interpretation and limitations
Neutrophilia can reflect sterile pustular inflammation or infection. Interpret patterns serially with examination, cultures, fluid balance and medicine history rather than using CRP alone.
03
Blood, pustule, erosion and other cultures when indicated
Why
Find secondary bacterial, fungal or viral infection and guide antimicrobial narrowing.
Interpretation and limitations
Collect before antimicrobials when this causes no unsafe delay. A sterile pustule culture supports but does not prove pustular psoriasis, and colonising growth requires clinical interpretation.
04
Pregnancy test and conception history
Why
Identify pregnancy-associated pustular disease and prevent exposure to teratogenic systemic treatment.
Interpretation and limitations
A positive test changes maternal-fetal monitoring and medicine choice immediately; do not rely on assumed infertility or age without respectful discussion.
05
Skin biopsy from a representative fresh lesion
Why
Differentiate pustular psoriasis, AGEP, lymphoma, PRP or blistering disease when morphology and timeline remain uncertain.
Interpretation and limitations
Histology complements rather than replaces clinical chronology. Obtain consent and ask dermatology to choose a useful site; results must not postpone stabilisation.
06
ECG, chest imaging or cardiac biomarkers when clinically indicated
Why
Assess arrhythmia, pulmonary oedema or high-output cardiac stress in a compromised patient.
Interpretation and limitations
These are consequence-directed tests, not routine diagnostic tests for psoriasis; interpret them against fluid replacement, renal function and pre-existing cardiac disease.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Acute generalised exanthematous pustulosis

AGEP is usually a rapid drug-related eruption with numerous small non-follicular pustules, often starting in folds, with neutrophilia. Medicine latency and histology help distinguish it from pustular psoriasis.

Severe cutaneous adverse reaction

Skin pain, mucosal erosions, dusky targetoid lesions, blistering, detachment, facial oedema or organ injury suggests SJS/TEN or DRESS and changes both culprit management and specialist pathway.

Infection

Staphylococcal infection, candidiasis, disseminated herpes and necrotising soft-tissue infection can complicate or mimic inflammatory disease. Sample appropriate sites but never delay sepsis treatment for results.

Other erythrodermas

Severe eczema, pityriasis rubra pilaris, pemphigus, crusted scabies and cutaneous lymphoma can generalise. Islands of sparing, lymphadenopathy, palmoplantar keratoderma and blood-film abnormalities redirect investigation.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ImmediateSame-day admission and stabilisationFirst stepGeneralised pustulation or near-total inflammation, particularly with systemic symptoms or abnormal observations.

1Call dermatology and acute medical services immediately, use ABCDE, establish monitoring and assess whether higher-acuity care is required.
2Measure input-output, urine, electrolytes, albumin, temperature and weight; give carefully titrated fluid and electrolyte replacement with cardiac and renal reassessment.
3Use bland emollient, gentle handling, non-adhesive dressings and a thermally controlled environment; avoid stripping scale or applying irritant active products across extensive skin.
4Take indicated cultures and start sepsis treatment promptly when infection is suspected; obtain analgesia, nutrition, thromboprophylaxis assessment and medication reconciliation.

02Diagnostic splitPsoriasis, drug reaction or infectionPustules or erythroderma with uncertain cause.

1Construct a day-by-day timeline of rash, symptoms, new or stopped medicines, infection, pregnancy and prior psoriasis phenotype.
2Examine mucosae, eyes, nodes, palms, soles and all skin for detachment, targets, islands of sparing, focal infection and residual plaques; calculate extent without depending on colour alone.
3Perform targeted histology and microbiology with explicit differential diagnoses, but continue supportive care and time-critical drug-reaction or sepsis action while awaiting results.

03Specialist systemic controlSuppress dangerous inflammationConsultant-confirmed unstable psoriasis after immediate supportive measures begin.

1Select treatment according to speed needed, phenotype, renal and hepatic function, infection, previous therapies and pregnancy potential; reconcile interactions before the first dose.
2NICE offers ciclosporin as the first-choice conventional systemic when rapid or short-term control is needed, using close blood-pressure, renal and interaction monitoring.
3Acitretin is a NICE option for pustular forms when appropriate, but its slow kinetics and profound teratogenic restrictions require specialist selection and the pregnancy-prevention programme.
4Review response and toxicity daily during instability; targeted immunomodulatory therapy follows current specialist guidance and commissioning rather than an improvised universal regimen.

04DischargePrevent rebound and readmissionPhysiology stable, skin improving and a safe ongoing plan agreed.

1EscalationDocument the most likely trigger, medicines stopped or continued, laboratory recovery, current systemic regimen, monitoring owner and exact escalation symptoms.
2Provide sufficient topical and systemic treatment, written dosing and rapid access if pustules, diffuse inflammation, fever or reduced urine recur.
3Coordinate dermatology, primary care, pharmacy and maternity or other specialties; never leave a systemic medicine without a named prescriber and monitoring schedule.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

NICE first-choice conventional systemic treatment when rapid or short-term psoriasis control is required, initiated and supervised by experienced specialists.

Ciclosporin for rapid specialist control

NICE uses 2.5 to 3 mg/kg/day orally in 2 divided doses; increase towards 5 mg/kg/day after 4 weeks only for non-response, or earlier when rapid control is necessary in severe unstable disease.

Check blood pressure, renal function, potassium, magnesium, infection, malignancy risk and interacting medicines; avoid unplanned combination immunosuppression and reduce to the lowest effective dose.

Specialist conventional systemic option when methotrexate and ciclosporin are inappropriate or have failed, and specifically for pustular forms of psoriasis.

Acitretin for pustular psoriasis

NICE targets 25 mg orally once daily using incremental dosing and permits escalation to a maximum 50 mg daily only when no other treatment option is available; assess response by 4 months.

Highly teratogenic: follow the current MHRA pregnancy-prevention programme, including contraception and testing for 3 years after stopping where pregnancy is possible; monitor lipids, liver and mucocutaneous toxicity.

Supports barrier comfort during stabilisation but does not replace systemic control, fluid management or antimicrobial treatment when infection is present.

Bland emollient

Apply generously and repeatedly by gentle smoothing to dry or fissured areas, using a non-irritant preparation and coordinating application with dressings and observations.

Extensive inflamed skin may sting with additives; residue on fabric and dressings increases fire severity, and greasy surfaces increase handling and fall risk.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Fluid and electrolyte loss

Insensible loss and exudation cause dehydration, acute kidney injury and sodium, potassium, magnesium or calcium disturbance. Replacement must be measured against cardiac and renal reserve.

Temperature dysregulation

Loss of normal barrier and vasomotor function can cause hypothermia or fever. Warmth, ambient control and repeated core temperature are part of treatment, not comfort extras.

Infection and thrombosis

Barrier breach, lines, immobility and systemic therapy increase bacterial infection and venous thromboembolism risk. Apply hospital prevention and surveillance according to current risk.

Cardiorespiratory strain

Peripheral vasodilatation, high output and fluid shifts can provoke heart failure or respiratory deterioration. Breathlessness and oedema require physiological assessment rather than reflex fluid loading.

Ocular and mucosal injury

True psoriasis usually spares mucosae; erosions or eye pain point toward drug reaction or another diagnosis and require early ophthalmic or mucosal specialist input.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

During acute illness, trend observations, core temperature, mental state, oxygen need, urine output, weight, fluid balance, electrolytes, renal function, liver tests, albumin and inflammatory markers at a frequency set by physiology.
Inspect skin daily for new pustules, detachment, focal infection and extent, documenting appearance across skin tones and photographing only with explicit consent and secure clinical handling.
With ciclosporin, monitor blood pressure, creatinine or estimated renal function, electrolytes, infection and interactions according to specialist protocol; rising creatinine or hypertension requires prompt action.
With acitretin, follow liver and lipid monitoring plus the complete MHRA pregnancy-prevention and testing schedule; record counselling and contraception decisions respectfully.
After discharge, provide an early dermatology review, named monitoring owner and same-day re-entry route for fever, recurrent generalised pustules, diffuse inflammation, oedema or oliguria.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Sterile does not mean safe

Pustular psoriasis can produce high fever and marked neutrophilia without infection, yet damaged skin also permits sepsis. Both possibilities must be managed concurrently until evidence separates them.

Oedema can mask depletion

Protein loss and inflammation may cause peripheral oedema while effective circulating volume falls. Use urine output, weight, renal tests and cardiorespiratory examination to guide replacement.

Mucosa redirects diagnosis

Prominent erosive mucositis is unusual in psoriasis. Mouth, eye or genital involvement should trigger urgent reassessment for SJS/TEN, autoimmune blistering or infection.

Withdrawal history matters

Ask what was stopped as carefully as what was started. Abrupt systemic corticosteroid withdrawal or interrupted effective psoriasis therapy can be the decisive precipitating event.

Colour scores can undercall

In deeply pigmented skin, heat, scale, tenderness, oedema and change from baseline may convey severity more reliably than a visual erythema score alone.

11Common pitfallsFrequent interpretation and management errors.

01
Waiting for biopsy confirmation before arranging same-day specialist care for a physiologically unwell erythrodermic patient.
02
Assuming every pustule is bacterial infection or, conversely, assuming established psoriasis excludes superimposed sepsis.
03
Giving large unmeasured fluid volumes without repeated cardiac, renal, weight and urine-output assessment.
04
Missing SJS/TEN or DRESS because all widespread inflammation in a person with psoriasis is labelled a flare.
05
Starting or stopping systemic corticosteroid without specialist ownership of the destabilisation risk.
06
Prescribing acitretin without applying current pregnancy-prevention requirements for the full post-treatment interval.