If you’ve been diagnosed with one of these conditions, there’s a good chance a provider has mentioned the other two — almost like a package deal. Patients and specialists have started calling it “the trifecta”: Ehlers-Danlos Syndrome (EDS), Postural Orthostatic Tachycardia Syndrome (POTS), and Mast Cell Activation Syndrome (MCAS).

Each is its own diagnosis, but they show up together often enough that understanding one usually means understanding all three.

EDS is a connective tissue disorder — it affects the collagen that gives structure to joints, skin, and blood vessels. POTS is a form of dysautonomia, where the autonomic nervous system doesn’t regulate heart rate and circulation normally, especially when standing. MCAS involves mast cells — immune cells that are supposed to protect the body — becoming overly reactive and releasing inflammatory chemicals like histamine too easily.