Recent advances in our understanding of mast cell activation - or should it be mast cell mediator disorders?
Theoharides, Theoharis C, Tsilioni, Irene, Ren, Huali · Expert review of clinical immunology · 2019 · DOI
Quick Summary
Mast cells are immune cells in your body that release chemical messengers (mediators) in response to many different triggers—not just allergies. When these cells release too many mediators, they can cause widespread symptoms affecting multiple body systems, including the brain and nervous system. This review suggests that doctors should look for elevated levels of these chemical messengers to help diagnose and treat these conditions, rather than waiting for the traditional markers (like histamine and tryptase) that don't always show up.
Why It Matters
Many ME/CFS patients experience multi-system symptoms (neurological, immune, gastrointestinal) that overlap with mast cell mediator disease, yet remain undiagnosed under existing criteria. This framework may help clinicians recognize and validate mast cell dysfunction as a potential mechanism in ME/CFS and guide development of targeted treatments beyond antihistamines. Expanding diagnostic criteria to include neuropsychiatric symptoms and diverse mediator profiles could improve identification and management of ME/CFS patients with underlying mast cell pathology.
Observed Findings
Mast cells release multiple mediators in response to immune, drug, environmental, food, infectious, and stress triggers, often without elevation of traditional markers (histamine and tryptase)
Multiple organ system involvement (brain, gastrointestinal, immune) occurs in patients with mast cell-mediated disease
Neuropsychiatric symptoms (including brain fog and autism-related features) are associated with mast cell mediator release
Diverse mast cell mediators (IL-6, IL-31, IL-37) are elevated in affected patients and contribute to multi-system inflammation
Inferred Conclusions
The current diagnostic framework for mast cell activation syndrome is too restrictive and excludes patients with significant mast cell mediator burden
Mast cell mediator disorders (MCMD) should be diagnosed by measuring multiple mediators rather than relying solely on tryptase or histamine
Neuropsychiatric and neurological symptoms should be recognized as legitimate manifestations of mast cell mediator disease
Future treatments should target the release of specific mast cell mediators rather than relying solely on antihistamine therapy
Remaining Questions
Which mast cell mediator profiles best predict clinical outcomes and treatment response in MCMD and ME/CFS populations?
What This Study Does Not Prove
This review does not directly demonstrate that mast cell mediator disorders are a primary cause of ME/CFS, nor does it establish causation between specific mediators and individual symptoms. The proposed MCMD diagnostic criteria have not yet been prospectively validated in clinical trials, and the study does not compare prevalence of mast cell mediators in ME/CFS populations versus healthy controls. The literature-based methodology cannot establish which mediator panels are most clinically relevant for diagnosis or prognosis.
How do validated diagnostic cutoffs for serum and urine mast cell mediators compare across populations, and what is the optimal testing methodology?
Which triggers (immune, infectious, environmental, stress) are most relevant to ME/CFS pathogenesis, and can they be used for personalized treatment strategies?
Do mast cell mediator levels correlate with symptom severity and functional impairment in ME/CFS, and can biomarker-guided therapy improve outcomes?