Characterization of flares in patients with generalized pustular psoriasis-A population-based study from the French National Health Data System database (SNDS)

Generalized pustular psoriasis (GPP) is a rare, neutrophilic skin disease characterized by recurrent episodes of widespread eruption of sterile pustules occurring with or without systemic inflammation and/or plaque psoriasis. Acute GPP flares can be severe and even life-threatening, and patient identification using administrative claims databases is difficult. This study aimed to develop an algorithm to identify and describe the characteristics of GPP flares using the French SNDS database (comprising data from 98.8% of the French population). A retrospective observational analysis of patients with GPP identified from 2010 to 2018 was conducted. Acute GPP flares were characterized from patient data using the following algorithm: treatment for GPP, with ICD-10 code L40.1 as the primary diagnosis in a medical, surgical, or obstetric inpatient setting, and hospitalization for ≥3 days. Overall, 1842 different incident patients with GPP were identified; of these, 30.9% (569) had ≥1 flare and 6.2% (115) had ≥2 flares during the study period, with patients experiencing an overall mean (standard deviation [SD]) of 1.4 (1.14) flares, with 1.26 (0.82) flares per person-year. Mean (SD) duration of hospitalization due to flares was 11.6 (10.5) days. All-cause mortality within the first 4 weeks after the last flare was 2.5%, and the median time to death [SD] was 15.64 days [7.97]. Up to the end of the study, all-cause mortality was 24.4%. Acute GPP flares defined in this study were associated with long hospitalizations. All-cause mortality was high (in patients with GPP flares). Further research is needed to clinically validate the flare algorithm.