Palmoplantar Pustulosis (PPP) is a rare form of psoriasis presenting with painful pustular eruptions localized to palms and soles. While PPP is potentially disabling, the factors that underlie disease severity remain poorly understood. To address this issue, we undertook a cross-sectional analysis of a deeply phenotyped British cohort (N=181; 41 males, 140 females; mean age of onset: 45.7 years).

Given that PPP shows a strong sex bias, we first examined disease severity in males vs females. While the age of onset was comparable in the two groups, the Palmo-plantar Pustular Psoriasis Area Severity Index (PPPASI) was significantly lower in males than females (4.3 vs 11.1; p=0.006), with a similar trend observed for the Dermatology Life Quality Index (3.5 vs 9.5; p=0.002). Next, we sought to assess whether smoking, a key risk factor for PPP, was also associated with severity. We found that the mean PPASI was high in current smokers, moderate in ex-smokers and low in non-smokers (13.1 vs. 11.1 vs 8.4, p=0.039).

To further explore this data, we conducted a hierarchical cluster analysis of 138 cases for whom data was available for a broad set of demographics (sex, ethnicity, smoking status, family history of psoriasis) and clinical variables (age of onset, PPPASI, concomitant psoriasis vulgaris, nail involvement).  

Using Gower’s distance, we identified 4 distinct patient clusters. In line with the above findings, one cluster was composed entirely of males suffering from mild disease (median PPPASI: 3.6). Of note, none of these individuals was a current smoker. 

While our results will require independent validation, they suggest that sex and smoking drive clinical differences in the presentation of PPP.

Sex and Smoke-Related Differences in the Severity of Palmoplantar Pustulosis