Teen receives devastating medical diagnoses after doctors dismiss symptoms as ‘anxiety’

At just 19 years old, Sydney’s teen Marissa De Santis spends most of her days in and out of the hospital, fainting up to five times a day, frequently seizing and battling chronic pain so intense it’s left her bedridden for weeks.

But despite her debilitating symptoms, doctors still dismiss her, telling her she “looks fine” and sending her home.

Marissa has Functional Neurological Disorder (FND), a complex and poorly understood condition that disrupts how the brain communicates with the body. FND affects movement, sensation, and even organ function — yet many medical professionals know little about it, and there’s no cure.

“I just want to be independent,” Marissa told news.com.au.

“People have no idea what it is. They look at me and think I look fine.”

Marissa’s symptoms started in high school. She struggled to concentrate, felt constantly sick, and was often sent home vomiting or in pain. In 2022, she managed to graduate, but months later her health took a steep dive.

She developed Postural Orthostatic Tachycardia Syndrome (POTS) that left her fainting every time she stood, sometimes collapsing on the stairs or in the shower. She’s had seizures that left her shaking violently on the floor, with her two most recent ones on Monday.

For five weeks earlier this year she was completely bedridden, unable to stand without passing out. She’s since been admitted to hospital for a week at a time — but doctors usually just check her vitals, give her some pain medication and send her home.

“No one really knows what to do,” she said. “I’ve had so many tests, they all come back fine.”

And that’s the kicker; People with FND do appear ‘fine’ on paper, but inside, their body is fighting for its life.

After seeing doctor after doctor and being told it was all in her head or it was ‘just anxiety’, Marissa began to lose hope.

“My body was shutting down, and I was overwhelmed and exhausted beyond words.

“Then one afternoon, everything changed — my body started shaking violently. I lost control. I had a full-body seizure. My eyes locked shut. I couldn’t speak, move, or cry for help.

“That was the moment I knew — this wasn’t just anxiety. It was real.”

Marissa’s younger sister Helena, now 17, was diagnosed with FND at just 14. Helena also collapses, suffers seizures and lives with chronic pain, though Marissa’s condition is more severe.

Their mother Sylvia said that although it hasn’t made it any easier, she was able to recognize Marissa’s symptoms earlier.

“It’s just heartbreaking,” said Sylvia.

“I want them to be better. There’s no help, there’s no answers, it’s so frustrating.”

“Marissa should be worrying about who she’s going to party with, not whether she can stand in the shower.”

“I just research and push doctors to listen. But I can no longer work or provide,” she said tearfully.

Sylvia has had to quit working for their family’s dog grooming business to take on the role of full-time carer in her home.

“We may need to look at selling our house. It’s a constant battle,” she says tearfully.

The family spends tens of thousands of dollars every year on weekly psychologists, fortnightly psychiatrists, cardiologists, neurologists, pain specialists, rehabilitation programs and even hypnotherapy.

Marissa is also taking over 10 medications to help manage her condition, including for her heart and seizures.

Earlier this year, Marissa was also diagnosed with autism level 2. Her care team believes autism contributed to her nervous system “overloading,” triggering the FND.

Marissa’s autism diagnosis has meant the family now has access to minimal NDIS support but FND and POTS are yet to be recognize on their own.

Recently, Marissa’s family surprised her with a visit from a service dog named Moose.

“When Moose visited Marissa, her heart rate dropped drastically,” said her mum.

Moose carries a hefty fee of $30,000 but will allow Marissa to regain a sense of independence and a better quality of life.

He will be able to notify her of oncoming seizures or fainting spells. He will also be able to press a doorbell that sends an alert in case of emergencies and assist Marissa in learning how to walk again using his walking frame.

Marissa has bravely spoken out about her condition for the first time, creating a GoFundMe to raise money to have access to Moose, who she says would be a lifeline.

“With a Moose by my side, I could reclaim parts of my life that I’ve lost — and maybe even feel safe enough to go outside on my own again,” she said.

Marissa says all she wants is a bit of awareness about what she’s going through.

“People have no idea what it is, but disabilities can be invisible. People often make a quick judgement but you can’t tell what’s going on inside someone’s head.”