DP28 The diagnostic challenge of distinguishing generalized pustular psoriasis from acute generalized exanthematous pustulosis

Abstract

Acute generalized exanthematous pustulosis (AGEP) is a severe cutaneous adverse reaction provoked by medications such as antibiotics and antiepileptics. Generalized pustular psoriasis (GPP) is a rare form of psoriasis. In both conditions, patients present with sterile pustules on a widespread erythematous rash, and systemic involvement, characterized by fever and organ dysfunction, can also occur. Histopathologically it is not possible to reliably distinguish between AGEP and GPP, as both can display neutrophilic subcorneal pustules with background spongiosis. We report the case of a 21-year-old woman who presented four times in 10 months (February, May, September and November 2025) with a spontaneous generalized pustular eruption, developing over the course of 5–7 days. She had no significant medical history, allergies, medication history or family history. Extensive history taking and investigations revealed no notable trigger. Two presentations required admission to the intensive care unit for respiratory and blood pressure support, and blood tests demonstrated hepatic derangement. Following hospital admissions of up to 14 days, she made full recoveries with supportive care. The first punch biopsy in February 2025 specifically highlighted that the findings were most consistent with AGEP rather than GPP. The pathologists concluded that the second punch biopsy in September 2025 also appeared to be in keeping with AGEP, but GPP should be considered based on the clinical context of recurrent presentations. This case highlights a dermatological diagnostic challenge: two conditions that are difficult to distinguish both clinically and histopathologically. The diagnosis of GPP is favoured over AGEP in recurrent presentations but consequently delays patient diagnosis and management. Clinicians should consider both conditions in new cases of spontaneous generalized pustular eruptions.