Association of the inflammatory marker suPAR with chronic pruritus of unknown origin - data from the SOMA.PRU study

Chronic pruritus (CP) is a frequent and burdensome dermatological symptom that can occur both in skin conditions such as chronic atopic dermatitis (cAD) and as CP on non-lesional skin of unknown origin (CPUO). Mechanisms of pruritus chronicity remain poorly understood. In line with other persistent somatic symptoms, chronic systemic inflammation may play a role in CP. Soluble urokinase plasminogen activator receptor (suPAR) has been proposed as a marker of long-term systemic inflammation, but has not yet been studied in relation to CP.

To study serum levels of suPAR in patients with CPUO in comparison to cAD and to study possible associations between suPAR levels and prospective clinical course.

We analyzed data from 105 participants (35 CPUO, 40 cAD, 30 controls). Clinical and patient-reported outcomes were collected at baseline and at a six-months follow-up visit.

Patients with CPUO had the highest suPAR levels in our study (3.2 ± 2.5 ng/ml), showing a non-significant trend toward higher levels than controls (2.9 ± 1.1 ng/ml) and, despite similar pruritus intensity, significantly higher than participants with cAD (2.0 ± 0.9 ng/ml, p = 0.018). Additionally, CPUO participants with higher levels of suPAR at baseline had higher average and worst pruritus intensity in the follow-up visit.

This study indicates that systemic chronic inflammation is a relevant aspect of CPUO. In particular, we infer that suPAR may be a biomarker associated with the longitudinal course of CPUO.