Itching Sensation and Elevated Interleukin-31 Levels as Potential Indicators of Exceptional Response to Biologics in Patients With Moderate-To-Severe Psoriasis

Although the introduction of biologics has significantly changed the psoriasis treatment paradigm, predicting which patients will respond favourably to biologics remains a challenge. Our study aimed to retrospectively investigate the characteristics of ‘exceptional responders’ (ERs), that is, patients who achieve a Psoriasis Area and Severity Index (PASI) of 100 between weeks 16 and 28 of their initial evaluation period. We conducted a retrospective analysis of the electronic medical records and clinical photographs of 139 patients with psoriasis. Demographic and clinical characteristics of the patients were collected and analysed. Peripheral blood samples previously obtained from consenting individuals (n = 10 for each group) were used to compare the serum concentrations of interleukin-31 (IL-31), lipocalin-2 (LCN2) and chemokine ligand 2 (CCL2), between ERs and non-ERs. We observed no significant differences in nail involvement, arthralgia, mean body mass index, or baseline PASI between ERs and non-ERs. Notably, the occurrence of itching was significantly higher in the ER group than in the non-ER group. The IL-31 concentration displayed a concomitant increase with the intensity of itching and was significantly higher in ERs than in non-ERs prior to the initiation of biologics. After treatment, a significant decrease in IL-31 levels was observed in the ER group but not in the non-ER group. While both LCN2 and CCL2 levels decreased significantly after treatment in both groups, they did not exhibit clear distinctions that could differentiate between ERs and non-ERs. Baseline IL-31, combined with itch intensity, discriminated ERs from non-ERs. Clinicians should recognise that patients presenting with pruritus and high serum IL-31 levels may respond exceptionally well to biological agents, whereas those without pruritus and with lower IL-31 levels tend to have a more subtle response.