Clinical characteristics of Japanese pustular psoriasis: A multicenter observational study

Generalized pustular psoriasis (GPP) is a rare and severe subtype of psoriasis. Because of its rarity, GPP studies with a large sample size have been scarce. We studied the characteristics of GPP and pustular psoriasis using data from the West Japan Psoriasis Registry that had been registered until the end of December 2020. The dataset included 104 patients with pustular psoriasis and 1290 patients with other subtypes of psoriasis. Multivariate analysis revealed a significantly greater number of female patients, a significantly lower mean body mass index, and a significantly lower ratio of habitual drinkers in pustular psoriasis, compared to other subtypes of psoriasis. Of the 104 patients, 102 had GPP, including 88 von Zumbusch, 10 juvenile-onset, and four annular pustular psoriasis. Although the male : female ratio of GPP with psoriasis vulgaris (GPP+PsV) (47/20) was similar to that of psoriasis in Japan, the GPP without PsV (GPP-PsV) group highlighted a female predominance (13/22). The mean age at GPP onset was 45.3 years, and the mean interval from PsV onset to GPP onset was 12.5 years. Four of nine patients with GPP had an IL36RN gene mutation. Infection, medicine, and pregnancy were the precipitating factors for GPP. A family history of psoriasis was present in eight (7.8%) patients with GPP. Twenty-four patients with GPP had psoriatic arthritis. Biologics were used in 76.5% of patients with GPP, followed by etretinate (37.3%), cyclosporine (24.5%), methotrexate (13.7%), apremilast (8.8%), and granulocyte and monocyte adsorption apheresis (6.9%). Etretinate was used in 17 (51.5%) of 33 patients with GPP with less than 10-year history. Thus, etretinate remains a good treatment option for GPP even in the era of biologics. Hypertension was the most commonly identified comorbidity, followed by diabetes. We believe that the characteristics revealed in this study can further contribute to effective GPP management.