If you’ve been searching for the cause of your unexplained severe abdominal pain and other symptoms—such as muscle weakness, nausea or vomiting, constipation, rapid heart rate, or emotional changes—there’s something you should know: these may be signs of a rare, serious disease called Acute Intermittent Porphyria (AIP). Learn more about this painful condition–and get closer to finally putting a name to the pain.