Generalised pustular psoriasis

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

Generalised pustular psoriasis is a rare psoriasis phenotype driven by dysregulated innate inflammation, especially the interleukin-36 pathway. It presents in flares of superficial non-follicular pustules that coalesce into lakes of pus and then desquamate, often in repeated waves. Fever, rigors, fatigue, oedema, pain and arthralgia can dominate. Disease may occur with or without plaque psoriasis and regardless of an identifiable IL36RN variant. Because visible redness varies with melanin, document pustulation, warmth, tenderness, oedema and extent rather than relying on a pink background.

A flare is both dermatological and medical. Massive inflammation and barrier disruption cause heat, water, electrolyte and protein loss; cytokine effects can produce leukocytosis, acute-phase elevation and organ dysfunction. Hypocalcaemia can precipitate or complicate pustulation. Infection can trigger GPP and broken skin can then become infected, so sterile pustules do not make cultures or sepsis treatment unnecessary. Conversely, antibiotics alone will not control sterile IL-36-driven inflammation. Pregnancy-associated generalised pustular psoriasis needs coordinated obstetric, dermatology and neonatal expertise.

Diagnosis integrates morphology, course, drug timing, cultures and histology. Initial care does not wait for a mutation result. After stabilisation, choose flare therapy from current specialist guidance, contraindications and speed needed. Spesolimab blocks IL-36 receptor signalling and can clear pustulation quickly in eligible flares, but the pivotal trial excluded immediate life-threatening or intensive-care flares. Conventional options such as ciclosporin remain important where rapid control or an alternative is needed. Long-term prevention is planned only after trigger review and recovery.

Key points

Generalised pustular psoriasis causes widespread visible or superficial non-follicular pustules on inflamed skin with systemic illness; pustules are sterile unless secondary infection complicates them.
Pustules may be conspicuous cream-yellow in any skin tone, while background erythema can look red, violaceous, grey-brown or dusky and is assessed with warmth, tenderness and swelling.
Ask about established plaque or pustular psoriasis, previous flares, pregnancy, infection, hypocalcaemia, medicine exposure and abrupt withdrawal of systemic corticosteroid or other psoriasis treatment.
Do not dismiss fever and neutrophilia as infection or psoriasis alone: culture plausible sites and blood in systemic illness while simultaneously treating physiological compromise.
AGEP is the key medicine-related mimic, often appearing rapidly after a drug with superficial flexural pustules, eosinophilia and quicker resolution after withdrawal; overlap still needs biopsy and specialist review.
Admit significant widespread disease for repeated temperature, haemodynamic, respiratory, urine, blood-count, renal, liver, albumin, calcium and inflammatory assessment.
Supportive care includes a warm environment, gentle bland emollient, fluid and electrolyte correction, nutrition, thrombosis and pressure care, and prompt directed antimicrobial treatment when infection is suspected.
Never use or withdraw systemic corticosteroid casually in psoriasis; withdrawal is a recognised precipitant and rescue treatment needs an experienced dermatology team.
NICE TA1070 recommends intravenous spesolimab for defined moderate-to-severe adult flares under specific GPPGA, fresh-pustule and body-surface criteria, including a separate subsequent-flare rule.
The current intravenous SmPC licenses flare treatment from age 12, but NICE funding is narrower; licence, appraisal, life-threatening-disease evidence limits and local specialist access must all be distinguished.

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

IL-36 pathway susceptibility

Variants affecting IL36RN and related innate-immune regulators occur in some patients, but many clinically confirmed cases have no identified monogenic cause.

Psoriatic inflammatory background

GPP may occur with previous plaque psoriasis, isolated recurrent pustular disease or a family history, reflecting interacting innate and adaptive immune susceptibility.

Treatment and medicine trigger

Abrupt systemic corticosteroid or psoriasis-treatment withdrawal can provoke a flare, while a newly introduced medicine may instead cause the phenotypic mimic AGEP.

Physiological trigger

Infection, pregnancy, hypocalcaemia and physical stress can precipitate innate inflammatory activation; sometimes no trigger is found despite careful reconstruction.

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

1
IL-36 signalling escapes restraint
Excess IL-36 receptor activation amplifies keratinocyte and immune-cell inflammatory loops when endogenous antagonism or downstream regulation is insufficient.
2
Neutrophils enter epidermis
Chemokines recruit large numbers of neutrophils into superficial epidermis, producing macroscopically visible sterile pustules that merge and recur in waves.
3
Barrier surface fails
Confluent inflammation, pustulation and desquamation increase evaporative loss, topical absorption and microbial entry while removing protein and impairing temperature control.
4
Cytokines affect organs
Systemic inflammatory mediators drive fever, vasodilation, capillary leak and high metabolic demand, which can progress to circulatory, renal, respiratory or cardiac dysfunction.
5
Calcium interacts with epidermis
Low calcium can alter epidermal differentiation and neutrophilic inflammation, acting as a trigger or complication that perpetuates pustulation if not corrected.

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

Acute pustular wave

Numerous superficial non-follicular pustules appear over broad tender inflamed areas, merge into lakes and desquamate while new crops continue at the edge.

Systemic inflammatory illness

Fever or hypothermia, rigors, fatigue, tachycardia, oedema, arthralgia and marked neutrophilia may accompany the skin eruption and precede organ dysfunction.

Skin-tone variation

Cream or yellow pustules and scale remain visible, but background inflammation may be red, purple, grey-brown or subtle; palpated heat and oedema clarify extent.

Psoriasis context

Previous plaque disease, nail pitting, a prior identical flare or recent withdrawal of systemic corticosteroid, ciclosporin or another effective treatment supports GPP.

AGEP context

A newly introduced medicine, short latency, flexural accentuation, facial oedema, eosinophilia and rapid improvement after withdrawal support acute generalised exanthematous pustulosis.

Pregnancy-associated flare

Generalised pustulation during pregnancy can threaten maternal fluid, electrolyte and placental function and requires immediate joint obstetric and dermatology assessment.

Organ-threatening flareRed flag

Hypotension, hypoxia, confusion, oliguria, marked calcium disturbance, tetany, extensive erosion or rapidly escalating oxygen and fluid need indicates critical illness.

Red flags requiring action

Hypotension, hypoxia, confusion, oliguria, rapidly spreading painful pustulation, hypothermia or high fever, severe oedema, tetany, mucosal involvement, pregnancy, childhood, frailty, neutropenia, suspected sepsis or respiratory symptoms requires critical-care-level reassessment and urgent specialist treatment.

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
Full blood count and differentialFirst step
Why
Quantify neutrophilic inflammation and identify eosinophilia, cytopenia or infection risk.
Interpretation and limitations
Neutrophilia supports systemic inflammation but does not distinguish sterile GPP from infection; eosinophilia and an implicated medicine increase AGEP or DRESS probability.
02
Renal, liver, bone and protein profile
Why
Detect organ injury, dehydration, electrolyte triggers and protein loss.
Interpretation and limitations
Trend creatinine, electrolytes, calcium, magnesium, phosphate, liver tests and albumin; check ionised calcium when symptoms or low albumin make corrected values unreliable.
03
CRP, cultures and infection assessment
Why
Identify a trigger or secondary sepsis without misclassifying every sterile pustule.
Interpretation and limitations
Obtain blood cultures in systemic illness and targeted pustule, wound, urine or respiratory samples; start sepsis treatment on physiology while interpreting growth against sampling site.
04
Skin biopsy
Why
Distinguish psoriasiform pustulation from AGEP, infection, pemphigus or another neutrophilic disorder.
Interpretation and limitations
A fresh untreated pustule and edge can show spongiform pustules and psoriasiform change; correlate eosinophils, necrosis and clinical timing because histological overlap occurs.
05
GPPGA and body-surface assessment
Why
Record flare severity and determine current NICE spesolimab eligibility.
Interpretation and limitations
Score total GPPGA and pustulation separately, document fresh or worsening pustules and percentage erythematous area with pustules, explicitly accounting for less visible erythema in darker skin.
06
Medicine and withdrawal timeline
Why
Find drug-induced pustulosis and prevent treatment-withdrawal amplification.
Interpretation and limitations
Record prescription, hospital, injectable, over-the-counter and complementary exposures with start, dose change and stop dates; identify systemic corticosteroid or psoriasis-treatment withdrawal immediately.
07
Pregnancy and specialist baseline screen
Why
Select systemic treatment and identify pregnancy-specific risk.
Interpretation and limitations
Test when biologically relevant and obtain agent-specific TB, hepatitis, HIV, blood pressure, lipids or reproductive assessments without delaying emergency supportive care.

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

Rapid medicine-induced pustulosis

Short drug latency, flexural onset, facial oedema, eosinophilia and rapid improvement after withdrawal favour AGEP, although morphology and histology can overlap.

Bacterial or fungal infection

Follicular pustules, focal tenderness, purulence, positive deep culture or sepsis source supports infection, which may also coexist with a sterile GPP flare.

Subcorneal pustular dermatosis

Chronic relapsing flaccid half-pustules in flexures with less systemic illness suggest Sneddon–Wilkinson disease and prompt paraprotein assessment.

IgA pemphigus

Annular or circinate vesiculopustules with characteristic intercellular IgA on direct immunofluorescence distinguish this autoimmune blistering disorder.

Pustular vasculitis or neutrophilic disease

Purpura, ulceration, arthritis or systemic inflammatory clues can indicate vasculitis, Sweet syndrome or another neutrophilic dermatosis requiring correctly sited biopsy.

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

01First-line emergency careAdmit, stabilise and sampleFirst stepFirst lineWidespread pustulation is accompanied by systemic symptoms, rapid progression or diagnostic uncertainty.

1Assess ABCDE, core temperature, haemodynamics, oxygen need, mental state, pain, extent, mucosae and urine output and involve dermatology immediately.
2Obtain full blood count, renal, liver, albumin, calcium, magnesium, CRP and appropriate cultures, biopsy a fresh lesion and document the complete medicine timeline.
3Nurse warm, use gentle bland barrier care, correct fluid and electrolytes against serial findings, support nutrition and treat clinically suspected sepsis promptly.
4EscalationAvoid abrupt systemic corticosteroid withdrawal and escalate pregnancy, organ failure, respiratory deterioration or shock to the relevant acute and critical-care teams.

02Gold-standard eligibility sequenceApply the live spesolimab criteriaAn adult has a confirmed GPP flare and intravenous spesolimab is being considered under NICE TA1070.

1For an initial flare, confirm GPPGA total score at least 3, fresh or worsening pustules, pustulation subscore at least 2 and at least 5% surface erythema with pustules.
2For a subsequent flare after previous spesolimab response, confirm fresh or worsening pustules and a GPPGA pustulation subscore of at least 2.
3Exclude clinically important active infection and active TB, review previous hypersensitivity and recognise that immediate life-threatening or ICU flares were not studied.
4Confirm the commercial arrangement and specialist plan, record product and batch, monitor infusion and define day-8 reassessment and rescue criteria.

03Specialist systemic alternativeChoose rapid conventional controlAlternativeSpesolimab is unavailable, unsuitable, outside appraisal or not the chosen emergency strategy.

1Select treatment with an experienced dermatologist according to severity, pregnancy, infection, blood pressure, kidney and liver function and previous response.
2When ciclosporin is chosen for rapid control, establish blood pressure, renal function, potassium, magnesium, interactions and infection risk before or alongside urgent initiation.
3Set a response deadline and toxicity schedule and plan transition to a safer maintenance strategy rather than leaving emergency treatment open-ended.

04Recovery and preventionPrevent another abrupt flarePustules and systemic physiology are resolving after acute treatment.

1Continue surveillance for infection, desquamation, electrolyte disturbance, oedema and organ injury until intake, mobility, temperature and laboratory trends are stable.
2Identify infection, pregnancy, hypocalcaemia, adherence, medicine withdrawal and avoidable interaction triggers and communicate them across prescribing teams.
3Agree a written maintenance, taper, rescue and rapid-access plan using current appraisal and SmPC advice and report suspected adverse reactions through Yellow Card.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

IL-36 receptor blockade for a GPP flare; NICE recommends it for adults meeting its defined initial- or subsequent-flare criteria and commercial arrangement.

Intravenous spesolimab

Give 900 mg as a single intravenous infusion over 90 minutes; if flare symptoms persist, one additional 900 mg dose may be given 1 week later.

Do not initiate with clinically important active infection or active TB; monitor anaphylaxis and infusion reaction, record batch, avoid unplanned combination flare therapy, and recognise limited evidence in immediate life-threatening or ICU disease.

Rapid conventional systemic control when selected by dermatology for a severe pustular flare or when targeted treatment is unsuitable or inaccessible.

Ciclosporin

For adult severe psoriasis, use 2.5 mg/kg/day orally in two divided doses, increasing gradually if needed to no more than 5 mg/kg/day under specialist supervision.

Check blood pressure, kidney function, potassium, magnesium, infection and interacting CYP3A4 medicines; reduce or stop for sustained creatinine rise or uncontrolled hypertension and plan a time-limited course.

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

Sepsis and secondary infection

Barrier disruption, systemic therapy and vascular access permit cellulitis or bloodstream infection, while sterile inflammation can conceal early microbial deterioration.

Fluid and electrolyte failure

Evaporation, capillary leak and exfoliation cause dehydration, oedema, acute kidney injury, hypoalbuminaemia and calcium or magnesium disturbances.

Cardiorespiratory failure

Inflammatory vasodilation and metabolic demand may provoke high-output cardiac failure, pulmonary oedema, acute respiratory distress and oxygen requirement.

Pregnancy and fetal harm

Pregnancy-associated disease can cause placental insufficiency, fetal growth restriction, preterm birth, stillbirth and maternal electrolyte or organ compromise.

Treatment toxicity and recurrence

Infection, infusion reaction, kidney injury, hypertension and abrupt withdrawal can complicate therapy, while recurrent flares cause repeated admission and psychological burden.

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

Record pustule formation, GPPGA total and pustulation subscores, inflamed body-surface area and standardised photographs with consent, accounting for subtle erythema in darker skin.
Repeat temperature, pulse, blood pressure, oxygen saturation, mental state, pain, weight, fluid balance and urine frequently until systemic inflammation is clearly resolving.
Trend FBC, CRP, renal and liver function, calcium, magnesium and albumin; investigate an unexpected reversal rather than assuming a second inflammatory wave.
During spesolimab infusion observe for hypersensitivity, stop and treat serious reaction, record brand and batch, and assess infection and neurological symptoms after discharge.
At 1 week determine whether symptoms persist and whether the authorised additional intravenous dose is appropriate; do not schedule it automatically without clinical reassessment.
For ciclosporin, follow frequent early blood pressure and renal monitoring, electrolyte and interaction review and a documented transition or stopping plan.
After recovery, reconcile every stopped or restarted medicine and give the patient flare signs, rapid-access contact, vaccination advice and a safe plan that prevents abrupt withdrawal.

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

Pus need not mean bacteria

Neutrophilic pustules in GPP are usually sterile, yet infection can trigger or complicate a flare and must be assessed in parallel.

Background colour can mislead

Pustules, warmth, swelling and tenderness establish active extent when surrounding erythema is purple-brown or visually subtle in richly pigmented skin.

Licence exceeds one appraisal

The intravenous SmPC includes adolescents from 12 years with weight-based dosing, while NICE TA1070 recommends funded flare treatment for specified adults only.

Trial evidence has an acuity boundary

Immediate life-threatening and intensive-care flares were excluded from the pivotal intravenous study, so critical support and expert alternatives cannot be deferred to one infusion.

Mutation testing does not gate rescue

IL36RN variants explain part of susceptibility, but clinical benefit occurred regardless of mutation status and acute treatment does not await genetics.

Day eight is a reassessment

The second spesolimab dose is permitted when flare symptoms persist one week later; it is not a routine two-dose loading schedule for every patient.

11Common pitfallsFrequent interpretation and management errors.

01
Calling widespread pustules bacterial and providing antibiotics alone without urgent dermatology and systemic support.
02
Excluding GPP because background inflammation is not bright red in brown or black skin.
03
Stopping prednisolone or ciclosporin abruptly in a person with psoriasis without an expert replacement plan.
04
Diagnosing AGEP or GPP from eosinophilia or one biopsy alone instead of integrating drug latency and course.
05
Treating corrected calcium as definitive when hypoalbuminaemia, tetany or critical illness warrants ionised calcium assessment.
06
Equating the broad SmPC indication with automatic NICE eligibility and funded access.
07
Giving a second spesolimab dose automatically rather than reassessing persistent flare symptoms at one week.
08
Assuming spesolimab has proven efficacy in an immediate life-threatening ICU flare excluded from its pivotal trial.