Sensitivity to itch and pain in patients with psoriasis and rheumatoid arthritis

Symptoms of itch and pain in chronic inflammatory conditions of psoriasis (PS) and rheumatoid arthritis (RA) can highly affect patients' quality of life. Studies in other patient groups indicate that sensitivity to itch and pain is altered in line with the patient's main symptom of either chronic itch or pain, as a result of sensitization processes. This study directly compared whether patients with chronic inflammatory conditions associated with chronic itch or pain display a heightened sensitivity to itch and pain, respectively. Sensitivity to itch and pain was measured by applying stimuli of quantitative sensory testing (QST) in female patients with chronic itch due to PS or chronic pain due to RA. Levels of itch and pain evoked by the QST stimuli as well as the tolerance to the stimuli were determined. Patients with PS reacted to the stimuli with a higher itch response (histamine), while the patients with RA displayed a lowered tolerance to the stimuli (cold pressor test and mechanical stimulation) in comparison with the other patient group. In line with previous studies in other patient groups with chronic itch or pain, further support was found that somatosensory stimuli are processed in line with the patients' main symptom through generic sensitization processes, also in chronic inflammatory conditions such as PS and RA.