New findings suggest a surprising immune connection to chronic pain
Researchers at the University of Arizona are reporting a potential link between chronic pain and a relatively rare immune condition known as eosinophilia. In a small study of medical records, scientists found that 12% of chronic pain patients treated with spinal cord stimulation or implanted pain pumps showed elevated levels of eosinophils, a type of white blood cell. Eosinophilia, which is usually seen in less than 1% of the general population, signals an immune system that may be behaving abnormally.
The study and what eosinophilia means
Led by Julie Pilitsis, MD, PhD, professor and chair of the Department of Neurosurgery at the U of A College of Medicine – Tucson, the research examined the records of 212 patients who underwent spinal cord stimulation (SCS) or intrathecal drug pump implantation for high-impact chronic pain. Of the 114 patients who had routine blood tests within a month before treatment, 14 individuals exhibited eosinophilia. That figure translates to roughly 12%—a striking contrast to its occurrence in the general population.
“The condition typically affects fewer than 1 in 100 people, and we found 14 of 114, or roughly 12%, in this group had eosinophilia before treatment,” Pilitsis said. “Now we’re asking what is it about eosinophilia that might predispose someone to chronic pain? Should we be looking at this as a biomarker before and after treatment to see if the latter reduces the eosinophilia?”
What are eosinophils and why could they matter for pain?
Eosinophils are white blood cells that help defend the body against certain infections and play a role in allergic responses. Eosinophilia can occur in autoimmune and inflammatory disorders, and researchers are increasingly exploring how immune system activity interacts with chronic pain. While the Arizona findings do not establish a cause-and-effect relationship, they raise important questions about whether inflammation or immune signaling could influence pain perception or treatment outcomes.
Implications for treatment and future research
Currently, about 70% of spinal cord stimulation patients report some reduction in pain, yet there is variability in response. Pilitsis notes that the eosinophilia finding could help researchers identify potential predictors of who will respond best to certain therapies and whether adjunctive anti-inflammatory strategies might benefit some patients.
“We don’t know if this could be a marker to help identify patients who might do better or worse with treatment, and if inflammation plays a role,” Pilitsis said. “Could spinal cord stimulation reduce inflammation at some point?”
Context and next steps
The study did not find a direct link between eosinophilia and common inflammatory diseases like rheumatoid arthritis, suggesting that eosinophilia may reflect a distinct or nuanced immune process in the context of chronic pain. The team emphasizes that these results are preliminary and based on retrospective data. Prospective studies and larger cohorts will be needed to determine whether eosinophilia could serve as an actionable biomarker.
Co-authors include Dr. Martin Weinand and medical students Hanna Johnson and Avantika Mitbander from the University of Arizona, along with collaborators from Florida Atlantic University and the College of Medicine – Tucson. The research aligns with a growing interest in how immune factors intersect with pain pathways and neuromodulation technologies.
Why this matters for patients and clinicians
Chronic pain affects a substantial share of adults in the United States, with about 24.3% experiencing some level of persistent pain and roughly 8.5% living with high-impact pain that disrupts daily function. For patients undergoing invasive pain therapies such as SCS or intrathecal pumps, understanding immune background may eventually guide personalized treatment plans and monitoring strategies.
As scientists continue to probe the relationship between the immune system and chronic pain, this study offers a first step toward identifying biomarkers that could predict treatment response or reveal new therapeutic targets. The authors stress that more research is needed, but the potential to tailor therapies by immune profile represents a promising direction for the field.
