Doctors dismissed a young woman's heart-pounding adrenaline attacks as anxiety. She now has a deadly tumor.

• Miranda Edwards had pounding headaches and heart palpitations, but doctors told her it was anxiety.
• She was finally diagnosed with a rare adrenaline-secreting tumor when she was 19 years old.

Growing up, Miranda Edwards said she was used to a feeling of '"impending doom" that she couldn't explain.

In her teenage years, she was often sick and had trouble sleeping at night. But she didn't think much of it until she was 19, when she started experiencing episodes of brutal headaches, heart palpitations, and vomiting all at once.

"My head felt like it was in a vise and it was being squeezed," Edwards, now 32, told Insider.

Edwards visited her family doctor and told him something was seriously wrong. She was having headaches more days than not, and they were always accompanied by flushing and sweating that took hours to go away.

However, Edwards said her doctor told her she was probably partying too much and not sleeping enough. If the episodes continued, she could come back for more blood work while she was symptomatic.

It would be the first instance in a years-long battle to get doctors to take her seriously. Meanwhile, a rare tumor was growing bigger on her adrenal gland, one of two tiny structures that sit atop the kidneys,

She would later find out that the softball-sized tumor was causing her body to produce excessive amounts of adrenaline. The headaches, palpitations, and all of her nights spent feeling "wired" were symptoms of the hormonal imbalance.

Doctors told her she was just anxious — until she had a heart attack

Edwards was frustrated when she left the doctor's office.

"I was like, 'Did you not hear what I said? I'm on the bathroom floor convulsing, with no vision, vomiting, and truly feeling like I'm going to die,'" Edwards said. "At my age, I should not have to put away three- to four-hour blocks of time in order to recover from this mystery assault."

As she continued to express concern over her symptoms, Edwards said the word "anxious" began to follow her like a scarlet letter.

Then one night, when she was 19 years old, she was hit with "horrific" chest pain while taking a bath. It turned out to be a heart attack.

Edwards stayed in the hospital for four days, and she continued to feel like her doctors thought she was being dramatic. Yet almost as soon as she was discharged, she got a call telling her she would need to be admitted again — this time to the Ottawa Heart Institute. She would stay there for two months.

She was diagnosed with a rare type of tumor

Edwards said her doctors' overall tone changed when an endocrinologist entered the room and told her she had a rare tumor called a pheochromocytoma. It was a noncancerous tumor positioned atop one of Edwards' adrenal glands, and it was making more adrenaline than her body could handle.

The stress hormone had caused her to have a heart attack in the bath, as well as two small strokes that doctors hadn't noticed earlier.

According to the National Cancer Institute, pheochromocytomas usually occur in people aged 30 to 50. It's estimated to affect about eight in every million people, but it's even rarer for a teenager to be diagnosed.

In some patients like Edwards, these tumors cause "paroxysmal attacks" that involve high blood pressure, headaches, irregular heartbeat, and sweating. Edwards calls them "pheo attacks."

While many pheochromocytomas are benign and can be removed, others grow back or can spread to more parts of the body, making them deadly.

When her tumor came back, doctors initially didn't believe Edwards again

Doctors performed a surgery to remove Edwards' tumor, which was supposed to cure her adrenaline attacks. While they seemed to abate at first, her symptoms soon returned and got worse. A year after her surgery, Edwards said she would still have attacks just from standing up too long or walking too fast — and she gained 45 pounds in three months.

"I knew with every fiber of my being that something went wrong, or something had come back," she said. "It was like I went back into a twilight zone where everybody didn't believe me again."

After four more years of medical gaslighting, an MRI showed that her disease had traveled to other organs in her body, including her liver. In November 2014, she was given one to five years to live.

"The fact that it had the opportunity to go to my liver and become aggressive was purely due to the delay in diagnosis," she said.

Edwards shares tips for living with her illness on social media to inspire other patients

Despite her medical history, Edwards describes herself as a "naturally bubbly, positive, and really happy person."

She said she's felt anger at several points in her 13 years of illness, but she tries to channel it into "taking her power back" instead of feeling helpless. Through a blog she named "Pheo Vs Fabulous" — and more recently, a TikTok account with the same name — she has documented her own illness journey, from her first misdiagnosis to how she copes with her attacks now.

"Not everybody is as vocal and open with their suffering as I am," she said. "You have these people who are suffering in silence, and their loved ones are not believing them because the doctors are saying they're fine."

Her TikTok bio now reads "Terminal & THRIVING," because even though her disease is incurable, she has already lived longer than any doctor expected.

"What I'm sharing requires you to fight like hell for yourself, but not everyone has the ability to do that," she said.