Mastie

A word used by the chronically ill and/or invisible illness community to refer to people who are diagnosed with a mast cell disorder - generally either Mast Cell Activation Syndrome (MCAS) or mastocytosis. "Mastie" is a cute name to refer to the person diagnosed with the condition. It's shortened for easier usage.

"You have MCAS too? Wow, I've never met another mastie before!"