The Clinical Relevance of Mast Cell Activation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.
Rohrhofer, Johanna, Ebner, Lilian, Schweighardt, Johannes et al. · Diagnostics (Basel, Switzerland) · 2025 · DOI
Quick Summary
This study looked at whether mast cells—immune cells that release chemicals causing inflammation—play a role in ME/CFS. Researchers surveyed 687 ME/CFS patients and reviewed records from 383 others, finding that about 25% had signs of problematic mast cell activation. Importantly, patients with mast cell problems who received targeted treatment reported better symptom relief than those without mast cell involvement, suggesting this might be a treatable subtype of ME/CFS.
Why It Matters
ME/CFS lacks effective targeted treatments, and identifying mast cell activation as a common, treatable comorbidity could enable personalized treatment strategies for a significant subset of patients. This work provides evidence that stratifying patients by MCA status may improve clinical outcomes and guide therapeutic selection.
Observed Findings
Approximately 25.3% of ME/CFS patients met clinical criteria for mast cell activation syndrome (MCAS)
ME/CFS patients with MCAS and orthostatic intolerance reported significantly better symptom relief following mast cell-targeted treatment than those without MCAS (p<0.0001)
OI, particularly POTS, was significantly more common in ME/CFS patients with mast cell involvement in both cohorts
IF-channel inhibitors showed a trend toward better efficacy in MCAS patients (p=0.076), whereas beta blockers showed no significant difference in response
MCA prevalence appeared to increase over the disease course in followed-up ME/CFS patients
Inferred Conclusions
Mast cell activation is a frequent and clinically relevant comorbidity in ME/CFS populations
MCA involvement is strongly associated with higher prevalence of orthostatic intolerance, particularly POTS
Stratifying ME/CFS patients by MCA status may enable more personalized and effective treatment approaches
Mast cell-targeted therapies may be particularly beneficial for ME/CFS patients with concurrent MCAS
Remaining Questions
What objective biomarkers best identify MCA in ME/CFS patients, and how do they correlate with patient-reported symptoms?
What This Study Does Not Prove
This study does not prove that mast cell activation causes ME/CFS—it only shows an association. The observational design cannot establish causality, and the primary dataset relied on patient surveys rather than objective laboratory measurements. The study also cannot determine whether mast cell-targeted treatments would benefit all ME/CFS patients or only those with confirmed MCA.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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Does mast cell activation represent a primary pathophysiological driver in some ME/CFS patients, or is it a secondary consequence of other disease processes?
Which specific mast cell-targeted treatments are most effective for ME/CFS-related symptoms, and what are optimal dosing and duration strategies?
Can prospective, controlled trials validate whether treatment of MCA improves long-term outcomes in stratified ME/CFS populations?