BACKGROUND AND OBJECTIVES: Generalized pustular psoriasis (GPP) is a rare, chronic, potentially life-threatening skin disease. We aimed to establish criteria to accurately approximate GPP prevalence in Germany. METHODS: A retrospective analysis of the WIG2 health claims database (1/1/2016-31/12/2020) was conducted. Patients aged ≥ 12 years continuously enrolled in their statutory health insurance with one inpatient or confirmed outpatient diagnosis code for GPP (International Classification of Diseases, 10 RESULTS: From 2016-2020, 5,236 potential GPP cases were identified based on a recorded GPP diagnosis. The scenario of ≥ 1 GPP diagnosis yielded the highest prevalence (336-390 patients/million) followed by >
1 GPP diagnosis in ≥ 2 quarters (189-288 patients/million)
scenarios resulting in the lowest prevalence were diagnosis in ≥ 2 quarters AND two independent diagnoses (17-28/million) and diagnosis in ≥ 2 quarters AND two independent diagnoses or diagnosis by a specialist AND potential flare (58-61 patients/million). CONCLUSIONS: This study suggests that diagnosis in ≥ 2 quarters by a specialist or two independent physicians may be the most clinically robust and reliable criteria for estimating GPP prevalence
therefore, 50-100 patients/million may represent a reasonable prevalence estimate range for Germany.