Pustular psoriasis (PP) is a group of inflammatory skin conditions characterized by infiltration of neutrophil granulocytes in the epidermis to such an extent that clinically visible sterile pustules develop. Because of clinical co‐incidence, PP is currently grouped with psoriasis vulgaris (PV). However, PP and PV are phenotypically different, respond differently to treatments and seem to be distinct on the genetic level. In contrast to PV, the phenotypes of PP are not well defined. Descriptions of each form of PP are discordant among standard dermatology textbooks [Saurat Dermatologie 2016, Rook's Dermatology 2016, Fitzpatrick's 2012 and Braun‐Falco 2012], encumbering the collection of phenotypically well‐matched groups of patients as well as clinical trials. The European Rare and Severe Psoriasis Expert Network (ERASPEN) was founded to define consensus criteria for diagnosis, deeply phenotype large groups of PP patients, analyse the genetics and pathophysiology and prepare for prospective clinical trials. This work reviews historical aspects of these conditions, new genetic findings and presents our initial considerations on the phenotypes of PP and a consensus classification of clinical phenotypes that will be used as a baseline for further, prospective studies of PP. Generalized pustular psoriasis (GPP) is defined as primary, sterile, macroscopically visible pustules on non‐acral skin (excluding cases where pustulation is restricted to psoriatic plaques). GPP can occur with or without systemic inflammation, with or without PV and can either be a relapsing (>1 episode) or persistent (>3 months) condition. Acrodermatitis continua of Hallopeau (ACH) is characterized by primary, persistent (>3 months), sterile, macroscopically visible pustules affecting the nail apparatus. Palmoplantar pustulosis (PPP) has primary, persistent (>3 months), sterile, macroscopically visible pustules on palms and/or soles and can occur with or without PV.

Background: The assessment of the prevalence of diseases is of primary importance in planning health policies. No complete data on the prevalence of skin diseases across European countries are available.Objective: To estimate the prevalence of the most frequent skin conditions or diseases in 27 European countries (24 EU countries, plus Norway, Switzerland, and the United Kingdom).Methods: We conducted a population‐based study on representative and extrapolable samples of the general population aged 18 years or more in each of the 27 countries surveyed. Participants were selected using stratified, proportional sampling with a replacement design. Data were collected using a web‐based online survey. All participants were asked to fill in a questionnaire with sociodemographic data and to declare if they have had one or more skin conditions or diseases during the previous 12 months.Results: A total of 44 689 participants from 27 countries responded to the questionnaire, 21 887 (48.98%) men and 22 802 (51.02%) women. The proportion of participants who reported having suffered from at least one dermatological condition or disease during the previous 12 months was 43.35% (95% CI: 42.89%, 43.81%). The projection in the total population of the 27 countries included in the study resulted in 185 103 774 individuals affected by at least one dermatological condition or disease. Accordingly, we can estimate that more than 94 million Europeans complain of uncomfortable skin sensations like itch, burning, or dryness. The most frequent conditions were fungal skin infections (8.9%), acne (5.4%), and atopic dermatitis or eczema (5.5%). Alopecia, acne, eczema, and rosacea were more common in women, whereas men were more likely to suffer from psoriasis and sexually transmitted infections.Conclusion: Skin diseases are an important public health concern. Their high prevalence has to be taken into account in planning access to dermatological care to address patient needs.