Assessment of flare frequency and severity of generalized pustular psoriasis in Japanese patients: A retrospective chart review study

Abstract Background Generalized pustular psoriasis (GPP) is a rare and often refractory disease, and GPP flares can be life threatening. The rarity of GPP prevents the development and evaluation of effective GPP‐specific treatments and obstructs disease understanding. Objectives To evaluate the frequency and severity of GPP flares and the clinical background and treatment history of patients with GPP in Japan. Methods This retrospective, longitudinal, Japanese chart review study included patients diagnosed with GPP (according to Japanese Dermatological Association [JDA] diagnostic criteria), with ≥6 months of continuous observation within 10 years of protocol approval at study sites. Primary outcomes: the frequency and severity of GPP flares during follow‐up. Secondary outcomes: patient characteristics (at time of initial GPP diagnosis) and GPP treatment during follow‐up. Results Overall, 205 Japanese patients were included; 106/205 (51.7%) were male, 146/205 (71.2%) were aged <65 years. Few patients had a family history of GPP (7/155, 4.5%) or psoriasis‐related diseases (6/120, 5.0%). At baseline, 36.1% (74/205), 30.7% (63/205) and 33.2% (68/205) of patients had mild, moderate and severe GPP, respectively; GPP flares were reported by 177/205 patients (86.3%), which were mostly moderate in severity (52/205; 25.4%) or severe (99/205; 48.3%). During follow‐up, GPP flares were reported by 70/205 patients (34.1%): 47/205 (22.9%) had 1 flare and 23/205 (11.2%) had ≥2. Among the 106 flare events reported during follow‐up, 1 was mild, 55 were moderate and 50 were severe. The median time to first GPP flare was 7.7 years and the overall incidence of GPP flares during follow‐up was 11.5/100 person‐years. During follow‐up, topical treatment (195/205; 95.1%), systemic therapy other than corticosteroids (177/205; 86.3%) and biologics (163/205; 79.5%) were most frequently used. Conclusions During follow‐up, over one‐third of Japanese patients with GPP experienced mostly moderate‐to‐severe GPP flares, despite available treatments. There remains an unmet need for effective GPP treatment options.