Mast Cell Activation Syndrome (MCAS) in hEDS

Introduction

Mast Cell Activation Syndrome (MCAS) occurs when aberrant mast cells (common in hypermobility) release excessive amounts of histamine, cytokines, prostaglandins and other chemical mediators, triggering multi-system symptoms that can mimic allergies, anaphylaxis or autonomic dysfunction. Up to one-half of people with hypermobile Ehlers-Danlos syndrome (hEDS) appear to show evidence of MCAS, and the prevalence rises further when broader clinical criteria are applied, forming the now-recognised “hEDS-POTS-MCAS” triad. PMC

Because histamine and related mediators can amplify pain signalling, slow gut motility and destabilise blood-pressure, MCAS may magnify the very fatigue, dizziness and gastrointestinal issues already common in hEDS. Dr Stephanie Barrett’s integrated rheumatology-immunology practice is uniquely placed to disentangle these overlaps and offer cutting-edge, personalised care.

What is MCAS in hEDS?

In hEDS, stretchy connective-tissue may alter the way mast cells sit in skin, gut and blood-vessels, pre-disposing them to hyper-reactivity. Recent genomic work has identified variants in HLA-DRB1, MT-CYB and other immune-regulatory genes that could link collagen abnormalities to immune dysregulation.

When a trigger such as heat, stress, infection or certain foods is encountered, these sensitised mast cells “degranulate”, flooding local tissues – and sometimes the whole body – with histamine, tryptase, leukotrienes and prostaglandins. In hEDS this can worsen joint pain, provoke flushing, tachycardia or abdominal cramping, and perpetuate central sensitisation.

Symptoms of MCAS in hEDS

Skin – Flushing, hives, itching, easy bruising

Gastro-intestinal – Bloating, abdominal pain, diarrhoea or constipation, food intolerances

Cardio-respiratory – Palpitations, low blood-pressure, breathlessness, wheeze

Neurological / Cognitive – Brain-fog, headaches, light-headedness, anxiety

Musculoskeletal / Systemic – Diffuse pain, fatigue, temperature sensitivity

Symptoms often flare with heat, alcohol, high-histamine foods, infections or hormonal shifts and improve with antihistamines or lying flat.

How to get a diagnosis of MCAS

Dr Barrett follows the updated 2024 MCAS consensus framework:

Detailed flare history & trigger review – including food diary and orthostatic symptom log.
Baseline + flare blood tests – serum tryptase, plasma histamine, prostaglandin D₂; plus 24-h urinary leukotriene E₄ if collected within 4 h of a flare.
Physical examination from a rheumatologist is essential noting dermographism, joint hypermobility (Beighton score) and dysautonomia features.
Response-to-therapy criterion – documented improvement with H₁/H₂ antihistamines, mast-cell stabilisers or leukotriene blockers.

A formal diagnosis requires: recurrent severe symptoms in ≥ 2 organ systems, a > 20 % + 2 ng/mL rise in tryptase (or other mediator) during a flare, and clear improvement on anti-mast-cell therapy.

Treatment for MCAS in hEDS

1. Trigger Management & Lifestyle Foundations

Low-histamine / low-tyramine diet, sulphite-free wines, cautious exercise pacing.

Stress-modulation (breathing techniques, restorative yoga).

2. First-line Pharmacological Blockade

H₁ antihistamine – Cetirizine, Fexofenadine

H₂ antihistamine – Famotidine
Leukotriene antagonist – Montelukast

These agents “mop up” released mediators.

3. Mast-Cell Stabilisers

Cromolyn sodium can reduce GI pain, flushing and diarrhoea, though onset may take 2–6 weeks. NCBI
Ketotifen (UK specials pharmacy) offers combined H₁ blockade and stabilisation.

4. Advanced / Refractory Options

Omalizumab (anti-IgE) – a 2024 case series showed marked itch reduction in MCAS with normal tryptase.

Low-dose naltrexone for neuro-inflammation and pain amplification.

Biologic nutraceuticals (quercetin, luteolin) under medical supervision.

5. Neuromodulation with rTMS (Emerging)

Pilot data show repetitive transcranial magnetic stimulation can normalise histidine-related metabolites and dampen neuro-immune hyper-reactivity, suggesting a role in central sensitisation and mast-cell cross-talk. Dr Barrett offers dorsal-medial prefrontal cortex protocols adapted from her fibromyalgia programme to selected patients with debilitating brain-fog or pain flares.

7. Integrated Care for the hEDS–POTS–MCAS Triad

Where orthostatic intolerance or dysautonomia co-exist, hydration plans, compression garments and beta-blockers are co-ordinated with cardiology colleagues, ensuring medications do not trigger histamine release.

Ready to calm the chaos?

Unpredictable flushing, abdominal pain or anaphylactoid episodes can be frightening — but with expert, evidence-based strategies they can be tamed. Dr Stephanie Barrett combines state-of-the-art diagnostics, precise medication protocols and innovative neuromodulation to help patients with hEDS-related MCAS regain stability and confidence.

Book your pain/HSD/HEDS, dysautonomia MCAS/assessment today and take the first step toward balanced mast cells and a calmer life.