01OverviewDefinition, clinical context and the essential points that orientate the chapter.
AGEP appears abruptly with pinhead non-follicular pustules arising on widespread oedematous skin. Lesions may coalesce superficially, fever is common and blood neutrophils rise. Limited mucosal involvement can occur, but extensive painful mucosal loss or sheet detachment should reopen SJS and TEN. Fine peeling follows pustular resolution.
The core work is immediate culprit review plus exclusion of infection and generalised pustular psoriasis. Obtain history of psoriasis, recent withdrawal of systemic corticosteroids, fever source and every recent medicine. A fresh pustule biopsy often shows subcorneal or intraepidermal neutrophils with papillary oedema and eosinophils, but clinicopathological scoring is more reliable than one feature.
Clinical decisions in Acute generalised exanthematous pustulosis depend on trajectory and consequence. Re-examine evolving skin, repeat focused systemic assessment when the patient changes, and reconcile every result with morphology and timing; a normal early test cannot neutralise worsening pain, mucosal injury or organ dysfunction.
Key points
- AGEP causes dozens to hundreds of tiny non-follicular sterile pustules on oedematous erythema, often beginning in face or folds and spreading rapidly.
- Onset is usually abrupt after a new medicine, commonly an antibiotic, and fever with neutrophilia is frequent.
- Bright erythema may be less visible in deeply pigmented skin; detect oedema, tenderness, pustular texture and later superficial desquamation.
- Construct exact drug start, stop and dose dates because a short latency supports AGEP but varies by culprit and previous exposure.
- Culture representative pustules when infection is a real alternative, yet recognise that colonisation does not explain a classic sterile pattern.
- Most cases improve quickly after drug withdrawal and supportive topical care, but monitor renal, hepatic, respiratory and fluid status.
- Acute generalised exanthematous pustulosis must be assessed by lesion duration, onset, distribution, symptoms, mucosal findings, systemic physiology and the full medicine timeline rather than by colour alone.
- For Acute generalised exanthematous pustulosis, document the working diagnosis, excluded emergencies, uncertain culprit or trigger, treatment response and the exact safety-net given.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Rapid drug hypersensitivity
Antibiotics are frequent triggers and pustules often appear within one or two days, especially after previous exposure, although latency varies by medicine.
Other medicine triggers
Calcium-channel blockers, antimalarials and additional drugs have longer characteristic latencies, making a complete dated exposure history essential.
Non-drug mimics and triggers
Infection can produce pustular eruptions or provoke generalised pustular psoriasis, so drug timing must be reconciled with clinical and microbiological evidence.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Neutrophil recruitment
Drug-reactive T cells release chemokines that rapidly recruit neutrophils into superficial epidermis, forming numerous tiny sterile non-follicular pustules.
- 2Fold-predominant spread
Oedematous erythema and pustules often begin on face or major flexures before disseminating over trunk and limbs.
- 3Systemic inflammatory response
Fever, neutrophilia and occasionally renal, hepatic or pulmonary abnormalities reflect broader cytokine activation and can mimic bacterial sepsis.
- 4Rapid desquamating recovery
After culprit withdrawal, pustules usually resolve within days and superficial scale follows, with total recovery commonly within about two weeks.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Numerous tiny superficial pustules arise outside hair follicles on oedematous inflamed skin and can become confluent.
Face and intertriginous areas are often affected early before rapid trunk and limb dissemination.
Systemic temperature and a high neutrophil count commonly accompany the eruption and can resemble sepsis.
Pustules collapse and superficial peeling appears within days after the trigger is withdrawn.
Severe skin pain, extensive mucosal erosion, dusky targets or sheet detachment is not routine AGEP and needs emergency reclassification.
05InvestigationsWhat to request, why it matters and how to interpret it.
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
Dated medicine and infection timelineFirst step - Why
- Identify rapid culprit latency and any infectious trigger or alternative.
- Interpretation and limitations
- Include antibiotics given after fever began, because a treatment started for prodromal infection may be blamed incorrectly or may itself worsen the eruption.
- 02
FBC with differential and inflammatory markers - Why
- Document characteristic neutrophilia and screen systemic severity.
- Interpretation and limitations
- Eosinophilia may occur and does not automatically make DRESS; inflammatory markers cannot distinguish sterile inflammation from sepsis.
- 03
Renal, liver and respiratory assessment - Why
- Detect less common organ involvement and guide admission intensity.
- Interpretation and limitations
- Trend abnormalities until improvement; normal initial results may change during rapid generalisation.
- 04
Pustule microbiology when infection is plausible - Why
- Exclude bacterial or fungal pustulosis before immunosuppressive treatment.
- Interpretation and limitations
- Sample a fresh intact pustule; sterile culture supports but does not alone prove AGEP after prior antibiotics.
- 05
Skin biopsy and structured scoring - Why
- Support AGEP and distinguish psoriasis or epidermal necrolysis.
- Interpretation and limitations
- Correlate subcorneal pustules, epidermal changes and dermal eosinophils with morphology, latency and resolution rather than using histology alone.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Generalised pustular psoriasis
Personal or family psoriasis, recurrent sterile pustulation, typical plaques and a less convincing drug latency support a psoriasis flare, though overlap can be difficult.
DRESS syndrome
Longer latency, facial oedema, eosinophilia, nodes and sustained organ injury fit DRESS more than the abrupt neutrophilic AGEP pattern.
SJS or TEN
Prominent skin pain, dusky targets, mucosal erosion and sheet-like epidermal necrosis require emergency evaluation for SJS or TEN.
Disseminated infection
Follicular or deeper pustules, positive cultures, focal source and septic physiology support bacterial or fungal infection rather than sterile AGEP.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Probable AGEPWithdraw and assess severityFirst stepA new medicine is followed by abrupt non-follicular pustules, fever or neutrophilia without extensive necrolysis.+
- 1Stop plausible non-essential culprits, document exact timing and obtain same-day dermatology or acute-medical assessment when disease is generalised.
- 2AlternativeCheck blood count, renal, liver and physiology, culture when infection is plausible and biopsy if psoriasis or necrolysis remains a significant alternative.
- 3Provide emollient, cool dressings and a site-appropriate topical corticosteroid while monitoring the expected rapid cessation of pustulation.
02Unwell or diagnostically unstableTreat competing emergencies in parallelHypotension, organ dysfunction, severe pain, extensive detachment or an infectious source accompanies pustulation.+
- 1Perform ABC assessment, take appropriate cultures, begin sepsis treatment when clinically indicated and avoid assuming all fever is sterile.
- 2Involve dermatology and critical care, reassess mucosa and detached surface and manage fluid, temperature and nutrition in hospital.
- 3Reconsider generalised pustular psoriasis, SJS, TEN and disseminated infection as evolution, biopsy and microbiology become available.
03Recovery and preventionConfirm resolution and refine culpritPustules have stopped forming and superficial desquamation follows withdrawal.+
- 1Continue skin care and organ monitoring until fever, neutrophilia, renal or hepatic changes and active pustulation resolve.
- 2Rank culprit probability from latency and known associations, then create a precise allergy entry and written avoidance advice.
- 3Refer for specialist drug-allergy assessment when several essential medicines remain plausible; never arrange unsupervised re-challenge.
Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
Betamethasone valerate 0.1% cream
Apply a thin film once or twice daily to limited intact inflamed areas for the shortest effective period, with a licensed maximum course of four weeks.Avoid large denuded areas, face, flexures, genital skin, infection and occlusion unless specialist-directed; review atrophy, absorption and masking of progression.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Organ involvement
A minority develop acute kidney, liver or lung injury, so apparent superficial pustulation does not remove the need for systemic assessment.
Fluid and temperature disturbance
Widespread inflamed skin, fever and desquamation increase insensible loss and can destabilise frail or comorbid patients.
Diagnostic antibiotic escalation
Mistaking sterile AGEP for uncontrolled infection may add related antibiotics, prolong exposure and make the culprit timeline harder to interpret.
Repeat severe exposure
Imprecise documentation can lead to re-prescribing the causal medicine and a faster recurrent pustular eruption during a future treatment episode.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Record daily new-pustule formation, temperature, skin pain, detached surface, mucosal symptoms and physiological stability during acute AGEP.
- Trend neutrophils, creatinine and liver tests until improvement where systemic abnormalities were present.
- Confirm that the allergy record distinguishes the most likely culprit from antibiotics started after eruption onset.
- At every review of Acute generalised exanthematous pustulosis, record lesion evolution, new mucosal or systemic features, medicine changes, treatment adherence and adverse effects.
- Give a named route for urgent reassessment if breathing, circulation, fever, skin pain, blistering, facial swelling, reduced urine output or other organ symptoms develop during Acute generalised exanthematous pustulosis.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
The pustules are non-follicular
Follicle-centred lesions suggest bacterial folliculitis or another process and should make the examiner reopen morphology.
Latency depends on the medicine
Antibiotic-associated AGEP may arise very quickly, while some non-antibiotic triggers take longer and still fit.
Neutrophilia is not sepsis proof
AGEP itself creates fever and neutrophilia, but infection must be treated when physiology or source supports it.
Peeling can signal recovery
Superficial desquamation after pustules resolve is expected and differs from painful full-thickness epidermal necrosis.
Psoriasis history changes probability
Previous plaques or pustular episodes, recent systemic steroid withdrawal and recurrence without drugs support generalised pustular psoriasis.
11Common pitfallsFrequent interpretation and management errors.
- 01
Calling follicular infected pustules AGEP without examining lesion centres or obtaining indicated cultures.
- 02
Adding multiple antibiotics for sterile fever and thereby obscuring the original culprit sequence.
- 03
Diagnosing DRESS from any eosinophilia despite abrupt latency and neutrophilic pustules.
- 04
Missing generalised pustular psoriasis in a patient with plaque history or recent corticosteroid withdrawal.
- 05
Reassuring a hypotensive patient because AGEP usually resolves after drug withdrawal.