Generalized pustular psoriasis (GPP) is a severe rare skin disease characterized by widespread eruption of sterile superficial macroscopic pustules with or without systemic inflammation. Generalized pustular psoriasis flares may lead to life-threatening multiorgan complications, which highlights the need for rapid and accurate diagnosis. However, the rarity of the disease and its heterogeneous cutaneous and extracutaneous symptoms, and the resemblance of symptoms to other skin conditions, pose considerable challenges to the timely diagnosis and treatment of patients with GPP. Current laboratory tests used for GPP diagnosis are generally not GPP specific, and are mainly focused on the assessment of inflammatory markers and clinical and histopathologic features of GPP, and emerging genetic screening approaches. A differential diagnosis to distinguish GPP from other similar conditions requires careful assessment of the patient’s skin symptoms, potential disease triggers, medical history, histopathologic features, laboratory tests, and clinical disease course. The comprehensive interpretation of these assessments can be challenging owing to the lack of standardized global guidelines. While there is currently a lack of standardized international guidelines for the diagnosis of GPP, recent advances in our understanding of the genetics and pathogenesis of the disease have provided new opportunities to enhance diagnosis. In the future, defining specific GPP subtypes using genetic and histopathologic strategies will guide therapeutic decisions, allowing patients to achieve their treatment goals without delay. In this article, we provide an overview of the current diagnostic methods, differential diagnostic strategies, and future advances in the diagnosis of GPP, as well as features of GPP variants.

Hidradenitis suppurativa (HS) is a chronic relapsing skin disease localized mainly on the apocrine gland‐bearing areas. In Japan, HS is yet to be fully understood, and no criteria have been established for its diagnosis or severity assessment. The purpose of this study was to investigate and characterize HS in Japan. We conducted a nationwide questionnaire‐based study, in which Japanese diagnostic criteria were proposed. Question items included age, sex, disease duration, past history, family history, smoking status, disease severity scores (Hurley stage, modified Sartorius score and Physician Global Assessment [PGA] score), treatments, comorbidities and prognosis. We analyzed 300 patients (219 males and 81 females) diagnosed with HS based on our criteria. Average disease duration was 92.3 ± 6.82 months. Only 12 (4%) patients had a family history of HS. Disease severity was classified by PGA score (mild, 100 [33.3%]; moderate, 133 [44.3%]; severe, 34 [11.3%]; most severe, 29 [9.7%]) and Hurley stage (I, 69 [23%]; II, 109 [36.3%]; III, 121 [40.3%]). Disease severities based on PGA score and Hurley stage were positively correlated to modified Sartorius score using the Kruskal–Wallis test (P < 0.001, respectively). Patients with diabetes mellitus showed higher PGA scores (χ² = 10.977, P = 0.01185). Presence of axillary lesions related to higher PGA scores (χ² = 8.6378, P = 0.03452). The results in this study and previous studies indicate that Japanese HS patients have different backgrounds from those in Western countries, and are characterized by male predominance, higher incidence of Hurley stages II and III, higher PGA scores in patients with axillary lesions and much fewer familial cases.

Secukinumab, a fully human monoclonal antibody that selectively neutralizes interleukin‐17A, has been available for the treatment of moderate to severe psoriasis and psoriatic arthritis since February 2015 in Japan. Because there was a time gap after the previous approval of biologics for psoriatic disease indication, it was suggested that patients to be treated with secukinumab at its launch might have refractory disease symptoms. In order to assess the safety and effectiveness of secukinumab in those patients, a 52‐week, open‐label, multicenter, observational cohort study was conducted. In total, 306 and 250 patients were included in the safety and effectiveness analysis sets, respectively. Over half of patients had previously received biologics (56.9%). Adverse events, serious adverse events and adverse reactions were reported in 41.2%, 7.2% and 24.2% of patients, respectively. The most commonly reported adverse reactions were oral candidiasis (2.9%), consistent with those reported in clinical studies. In addition, none of the patient characteristics assessed for the effect on safety of secukinumab increased the occurrence of adverse reactions. Psoriasis Area and Severity Index score (mean ± standard deviation) improved from baseline (14.7 ± 12.3) to week 12 (1.78 ± 3.3), which was maintained up to week 24 (1.59 ± 3.0). The proportion of patients with a Dermatology Life Quality Index score of 0/1 improved from baseline (2.2%) to week 12 (64.7%) and sustained up to week 24 (71.4%). In addition to the skin symptoms, improvement was observed in all psoriatic arthritis disease‐related assessments. The current study reaffirmed the safety and effectiveness of secukinumab with broader patients than those in the clinical studies.

Generalized pustular psoriasis (GPP) is a rare variant of psoriasis with severe clinical symptoms. However, the quality of life (QoL) of the patients is largely unknown. We conducted a nationwide cross‐sectional survey of Japanese GPP patients using the 36‐Item Short‐Form Health Survey version 2 (SF‐36v2) to elucidate patients’ QoL and how their QoL had changed over the last decade. We analyzed QoL data of 83 patients obtained from 2016 to 2019 (present group) and compared it with that of 105 patients collected in a previous survey conducted between 2003 and 2007 (past group). Although the QoL of the present patients was still largely impaired in comparison with the standard Japanese population, substantial improvement was found in some SF‐36v2 subscales including “general health”, “vitality”, “social functioning” and “mental health” as compared with that of the past group. Advances in treatment may contribute to this QoL improvement.

Generalized pustular psoriasis (GPP) is a rare, chronic, heterogeneous, and potentially life‐threatening disease characterized by primary, sterile, and macroscopically visible pustules with or without systemic symptoms. There are ethnic differences in the genetic mutations associated with GPP that might affect the clinical manifestations and treatment responses. Currently, there is limited evidence from the patient population in the Asia‐Pacific (APAC) region, resulting in a general paucity of information on the effective management of patients with GPP in this region. This modified Delphi panel study aimed to identify current evidence and gain advanced insights to facilitate the development of a regionally tailored APAC consensus on the management of GPP. A systematic literature review (SLR) was conducted to identify published literature and develop consensus statements on (i) definition and clinical course, (ii) diagnosis of GPP, (iii) treatment outcomes, goals, and monitoring measures, and (iv) optimal management strategies and clinical practices. Statements were rated by a panel of dermatologists in two rounds, with the threshold for consensus at ≥80% agreement. Twenty experts from the APAC region reached consensus on 106 statements that were developed based on the SLR and experts' collective expertise. The experts agreed that GPP is a rare, severe, and potentially life‐threatening condition that is distinct from plaque psoriasis. This consensus emphasized the importance of a tailored treatment strategy taking into account the GPP flare severity and each patient's unique clinical circumstances. The experts reached consensus on the severity classification of GPP flares and recommended first‐line and maintenance treatment options for adult GPP, childhood GPP, and GPP in pregnancy. These consensus outcomes have been synthesized into treatment algorithms to guide dermatologists in the APAC region in their clinical decision‐making processes.