Real-world evidence on palmoplantar pustulosis: Patient characteristics, diagnostic challenges and predictive factors for treatment survival - a retrospective registry study

BACKGROUND: Little is known about the clinical characteristics, diagnostic delay and treatment survival in patients with palmoplantar pustulosis (PPP). OBJECTIVES: To analyse the survival rates of patients with PPP in Austria treated with phototherapy, conventional systemic therapies and biologics. METHODS: This was a retrospective study using data from the Psoriasis Registry Austria (PsoRA). The analysis included data collected between 16 May 1997 and 11 April 2024 from patients with PPP. RESULTS: We included data from 190 patients who underwent 397 treatments. Fifty-four per cent of patients (n = 37/69) were initially misdiagnosed as having eczema with a mean (SD) diagnostic delay of 2.8 (4.8) years. Patients were predominantly women (n = 141/190; 74.2%) and smoked (n = 76/98; 78%). Patients were treated with biologics (n = 198/397; 49.9%), phototherapy (n = 100/397; 25.2%) and conventional systemic therapies (n = 99/397; 24.9%). Median survival time for all treatments was 0.6 years [95% confidence interval (CI) 0.5-0.8], with patients on ustekinumab having the longest median survival time of 2.7 years (95% CI 2.3-upper limit not reached), surpassing all other therapies. This superiority disappeared after interleukin (IL)-23p19 inhibitors were introduced in Austria. Compared with biologics, conventional systemic treatments [hazard ratio (HR) 2.17; P < 0.001] and phototherapy (HR 4.43; P < 0.001) were associated with a significantly higher risk of treatment discontinuation. In the overall cohort, disease durations of ≥ 2 to < 10 years (HR 0.66; P = 0.05) and ≥ 10 years (HR 0.59; P = 0.004) significantly reduced the risk of treatment discontinuation, while concomitant plaque psoriasis significantly increased the risk of treatment discontinuation (HR 1.43; P = 0.05). In the biologic cohort, concomitant arthritis (HR 2.11; P = 0.002) and the presence of one comorbid disease (HR 2.34; P = 0.03) increased the risk of treatment discontinuation. Furthermore, sex, age at disease onset and smoking did not influence the risk of treatment discontinuation. CONCLUSIONS: Our findings suggest that more than half of patients with PPP experience a diagnostic delay of several years due to an initial misdiagnosis. Patients on ustekinumab (IL-12/23p40 inhibitor) had the longest treatment survival, although its superiority diminished with the introduction of IL-23p19 inhibitors. Finally, shorter disease duration and concomitant plaque psoriasis is a general risk factor for treatment discontinuation, while the presence of a comorbidity and concomitant psoriatic arthritis are risk factors for discontinuing biologics.