The hEDS / POTS / MCAS Triad

What the standard model gets wrong

The standard model treats the triad as three diseases that happen to co-occur. Rheumatology addresses the hypermobility. Cardiology addresses the POTS. Allergy or immunology addresses the MCAS. The co-occurrence is acknowledged epidemiologically and explained as unfortunate clustering, sometimes hand-waved as shared connective tissue substrate without further specification.

Each specialty treats its piece. The patient ends up on stabilizers, beta-blockers, salt and compression, physical therapy, and various adjuncts. The improvement in each domain plateaus, and the overall functional state remains constrained. The framework permits no unifying intervention because it does not posit a unifying lesion.

The unifying lesion is bioenergetic. The substrate is the same in all three cell populations. The interventions that target the substrate produce changes that the organ-system framework cannot predict.

What the Host Capacity Model says about the triad

Connective tissue fibroblasts, vascular endothelial cells, and mast cells are bioenergetically demanding. They depend on mitochondrial Complex IV activity, on adequate NAD+ pools, and on iron-sulfur cluster integrity in the electron transport chain. They are also highly responsive to inflammatory signaling, which means that any sustained inflammatory state reduces their bioenergetic margin further through CD38-mediated NAD+ consumption.

In patients with hypermobility spectrum genetics, fibroblast function is already constrained. The genetic substrate is unchanged. What is highly modifiable is the bioenergetic margin around that substrate. A NAD+-depleted hypermobile fibroblast produces more dysfunction than a NAD+-repleted one with the same genetics.

Vascular endothelial cells maintain tone, barrier integrity, and orthostatic compensation. Endothelial bioenergetic failure shows up clinically as POTS. The autonomic reading is downstream of the cellular reading.

Mast cells in this state are trip-wired for the reasons the refractory MCAS page lays out — barrier-driven endotoxin load, dysbiotic metabolite signaling, and CD38-driven NAD+ depletion making the cells both more excitable and worse at mediator clearance.

The triad is therefore one cascade with three readouts. Treating the cascade — restoring NAD+, supporting mitochondrial function, reducing inflammatory load through dysbiosis and barrier work — produces simultaneous improvement in all three phenotypes. The genetics do not change. The functional expression does.

Patterns I look for in cases like this

• All three diagnoses present, with the patient cycling through specialists.
• MCAS flares that intensify during POTS symptoms.
• Worsening joint instability during inflammatory or post-viral episodes.
• Post-exertional malaise on top of the POTS picture.
• Concurrent dysbiosis or SIBO history.
• Worsening of all three phenotypes after antibiotic courses.
• Onset or intensification of the triad after a viral event.
• NAD+ depletion on direct measurement.
• Disproportionate response to standing, heat, or large meals.
• A history of partial response to each specialty's intervention with no overall recovery.

Tests I usually want to see

• Intracellular NAD+ panel — often markedly low across this group.
• Organic Acid Test — bioenergetic flux and oxidative stress markers.
• Tryptase, urine N-methylhistamine, urine prostaglandin metabolites.
• Tilt-table or active stand testing — POTS confirmation.
• Barrier markers — zonulin, LPS, LBP, calprotectin.
• Shotgun metagenomics — sulfide producers, butyrate producers, gram-negative dominance.
• Ferritin, iron, copper — iron-sulfur and Complex IV context.
• hs-CRP, IL-6 — chronic activation panel.

Leverage points

The single highest-leverage intervention in this group is NAD+ restoration, sustained over months. CD38 is consuming NAD+ as long as inflammatory activation continues. Without addressing this, every other intervention is downstream rate-limited.

Dysbiosis and barrier work are second. The endotoxin load from a leaky, dysbiotic gut is what keeps the inflammatory activation high in the first place. Treating the gut is treating the cascade at its sustaining source.

Symptom-layer treatment continues throughout. Stabilizers for MCAS, beta-blockers and volume support for POTS, physical therapy for hEDS. These do not get withdrawn when upstream work begins. They get de-escalated as upstream improvement makes them unnecessary, which is months out.

Exercise is nuanced. Acute phase, recumbent only. Recovery phase, very gradual standing work. Maintenance phase, graded program with continued attention to flare risk. The common pattern is overestimation of capacity in the recovery phase, followed by setback. The protocol works best when pacing is honored.

Where this account may be wrong

Classical EDS subtypes with defined collagen mutations follow different trajectories and need different management. The bioenergetic account is strongest for hypermobile EDS in combination with POTS and MCAS. POTS without hypermobility or MCAS may have different primary mechanisms. The framework is offered for the recognizable triad, not as a universal account of any one diagnosis in isolation.

Frequently asked questions

Related reading

• The Host Capacity Model
• hEDS/POTS/MCAS overlap protocol
• Refractory MCAS
• Mitochondrial dysfunction
• Dysbiosis as upstream load