Generalised pustular psoriasis (GPP) is an uncommon but serious disease within the psoriasis family. GPP causes sterile pustules that affect the whole body (= generalised), often along with systemic symptoms. GPP can occur on its own, or together with psoriasis vulgaris, the most common type of psoriasis. It is not known how many people suffer from this condition around the world – the few studies available show a large variation in numbers. In this study, we used Swedish register data to find out how common GPP is. We also investigated how common it is to have GPP and psoriasis vulgaris at the same time.
The results showed that 9 out of 100 000 Swedish people had a GPP diagnosis and that 0.82 out of 100 000 were newly diagnosed with GPP during one year. However, these numbers decreased by approximately half when GPP diagnosis from at least two doctor’s visits were used as the criterion of having GPP. The study showed that more women than men suffered from GPP and that it was most common among people over 60 years. Forty-three percent of patients with GPP had also a diagnosis of psoriasis vulgaris.
The numbers found in this large Swedish study were within the range of earlier studies. However, the variation observed for the two different GPP diagnostic criteria (i.e. one or two diagnoses) used in this study highlight the need to use similar diagnostic criteria between studies to allow for comparisons.
British Journal of Dermatology, 2022. Online ahead of print.