Background

Generalised pustular psoriasis (GPP) is a severe form of pustular psoriasis with generalised eruption of sterile pustules, often along with systemic symptoms. There is a scarcity of population-based estimates of GPP prevalence and incidence.

Objectives

To estimate i) the prevalence and incidence of GPP in the Swedish general population and ii) the prevalence of psoriasis vulgaris within the GPP population.

Methods

We identified cases (2004-2015) with one ICD-10 diagnostic code (base case) for GPP within the Swedish National Patient Register, which covers inpatient and outpatient secondary care. Cases were linked to the Swedish Total Population Register and the point prevalence was estimated as on 31 December 2015. In two alternative analyses we changed case definitions to: 1) requiring two visits (strict case 1), 2) requiring two visits of which one within dermatology/internal medicine (strict case 2).

Results

The base case point prevalence of GPP was estimated to 9.1/100 000 (women=11.2, men=7.0) and the annual prevalence in 2015 was estimated to 1.53/100 000. Among the GPP population, 43% also had a psoriasis vulgaris code. The incidence of GPP in 2015 was estimated to 0.82/100 000 (women=0.93, men=0.74). The criteria used had an impact on prevalence and incidence estimates; prevalence strict case 1) 3.8/100 000 and incidence strict case 1) 0.42/100 000.

Conclusions

Results indicate that the estimated GPP population in Sweden is within the range of previous published estimates. However, the estimates were sensitive to employed GPP case criteria. The findings enhance demands for studies using validated diagnostic algorithms.