I'll never forget my doctor walking into the room and saying, David, your liver, your kidneys,

your bone marrow, your heart, and your lungs are shutting down. I was just treating patients down

the hall. I was just spiraling, not knowing what was actually happening, just being so confused,

because I had just talked to him like two days ago.

A priest came in and read him his last rites, and then a few of his friends came in and ultimately

hugged him goodbye.

I had to take some action, and it had to be like a crazy step,

and that is to start testing one of these drugs that I was studying in the lab on myself.

How terrifying would it be to fight an unknown enemy,

one you didn't recognize and didn't see coming.

What if that enemy was coming from within,

a disease that even doctors couldn't identify?

Nearly half of all Americans suffer from some chronic illness

and many struggle for an accurate diagnosis.

These are their stories.

I'm Lauren Bright Pacheco, and this is symptomatic. David Faganbaum grew up in Raleigh, North Carolina.

And I've got two older sisters, seven and five years older than me, and two amazing parents.

They immigrated to the United States from

Trinidad and Tobago in the Caribbean. So they were sort of making this new life, the American

dream in the States. And childhood exposure to a very American sport ignited one of David's

biggest dreams. And your dad is an orthopedic surgeon and worked for a period of time with North

Carolina State Wolfback team. That's right. Which is where at the age of seven, you had this

...