Prevalence and incidence of palmoplantar pustulosis in Sweden: a population-based register study

Löfvendahl S, Norlin J.M, Schmitt-Egenolf M

Palmoplantar pustulosis (PPP) is a chronic relapsing skin condition characterized by sterile pustules together with redness and scaling on the palm and soles, which erupt over time. Traditionally PPP has been classified as a subgroup of psoriasis as it is often seen in combination with psoriasis vulgaris. Smoking, infection, and certain drugs trigger or exacerbate the disease. Many of those suffering from PPP experience reduced Health-Related Quality of Life (HRQoL) and one study has reported that PPP is associated with greater impairment of HRQoL than moderate-to-severe psoriasis.

There are few published estimates of prevalence and incidence of PPP. Previous studies, with use of different case definitions and prevalence measures, show large variations (range from 50-120 per 100 000) in the estimates of PPP.

The objectives of the current study were to estimate the prevalence and incidence of PPP in the Swedish general population and to estimate the prevalence of psoriasis vulgaris among the PPP population. The Swedish National Patient Register, covering all inpatient and outpatient non-primary care for the Swedish population, was used. We identified cases (period: 2004-2015) with one ICD-10 diagnostic code (base case) for PPP. The point prevalence estimates at the end of this period (31 December 2015) were obtained by linkage to the Swedish Total Population Register. In sensitivity analyses, we used alternative case defintions:1) requiring two visits, 2) requiring two visits of which one within dermatology/internal medicine. The base case prevalence of PPP was estimated to be 147/100 000 (women=227, men=68) and the annual prevalence was estimated to 26/100 000 in 2015. Among the PPP population, 17% were registered with a diagnostic code for psoriasis vulgaris. The incidence of PPP in 2015 was estimated to be 12.7/100 000 (women=18.7, men=6.6). The criteria used had an impact on prevalence and incidence estimates; changing to the strict case 1 definition the prevalence decreased to 72/100 000 and the incidence to 5.4/100 000.

Results indicate that the population-based prevalence of PPP may be larger than previous estimated. However, the estimates were sensitive to employed PPP case criteria. The findings enhance demands for studies using validated diagnostic algorithms potentially also including data from the primary care setting. Comparisons of incidence and prevalence across studies must be done with caution due to methodology differences.

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British Journal of Dermatology, 2021; 185(5): 945-951
DOI: 10.1111/bjd.20087