Acute generalised exanthematous pustulosis

Sheets of small non-follicular sterile pustules studding bright oedematous erythema, beginning in the flexures, followed by desquamation as it resolves.

The pustules themselves are the tone-independent finding and remain visible as pale or yellow-white pinpoints, but the oedematous erythema underneath may not read as red at all - it can look darker, violaceous or simply swollen and shiny, so the classic description of pustules on a red base can be misleading. Feel for the oedema. Resolution leaves marked post-inflammatory hyperpigmentation with the desquamation.

• Onset within days of starting a drug - typically faster than DRESS
• Dozens or more small non-follicular pustules, sterile on culture
• Fever and neutrophilia
• Flexural onset
• Resolves with desquamation over one to two weeks after the drug stops - a conventional interval, not one stated by the EuroSCAR study cited below

• Stevens-Johnson syndrome / toxic epidermal necrolysis — Both acute drug reactions with fever; necrolysis detaches epidermis and erodes mucosa rather than forming pustules
• Generalised pustular psoriasis — The deferred link now closed. Generalised pustular psoriasis presents almost identically; a personal or family history of psoriasis does NOT distinguish them, because the EuroSCAR study found no increased AGEP risk with a psoriasis history. The drug timeline is the discriminator
• Erythroderma — Either condition can become erythrodermic

1. Stop the likely culprit - antibiotics dominate the list, with ampicillin and amoxicillin, quinolones, anti-infective sulphonamides, terbinafine, (hydroxy)chloroquine and diltiazem the drugs most strongly associated in the EuroSCAR case-control study. Its top-ranked drug, pristinamycin, is omitted here only because it is not marketed in the UK
2. Swab or aspirate a pustule: sterility supports the diagnosis and excludes bacterial pustulosis
3. Take FBC, liver and renal function - to confirm neutrophilia and to look for overlap with DRESS
4. Do not reach for systemic antibiotics for the pustules themselves; they are sterile and an antibiotic may be the cause
5. Discuss with dermatology. Admit if febrile and unwell, extensively involved, or if the diagnosis is not secure
6. Document the drug as a reaction and avoid re-exposure

Same-day dermatology. Admit if febrile, systemically unwell, extensively involved, if liver or renal function is deranged, or if epidermal necrolysis has not been confidently excluded - which, given that fever and neutrophilia are the rule in AGEP rather than the exception, will be most patients at first presentation.

• Sidoroff A et al. Risk factors for acute generalized exanthematous pustulosis (AGEP) - results of a multinational case-control study (EuroSCAR). Br J Dermatol 2007
• Lim HW et al. International Expert Consensus on Knowledge Gaps in Care for Dermatologic Disorders in Skin of Color. Int J Dermatol 2026
• NICE CG153 1.2.1.5 - erythema may be underestimated in skin types V-VI (stated in the psoriasis guideline; cited here for that general point about assessing erythema, not for this condition)