If you know Matthew Inn, you wouldn’t believe it.

He’s a healthy 20-year-old who loves to run, skateboard and work out. He even eats organic food.

But this summer, while he was living in Portland with his sister, he had a couple of fainting spells. He went to the doctor who diagnosed him with low blood pressure. Nothing unusual. But he started to feel weaker. He couldn’t run as far or as hard. So his parents, Jan and Clifford, urged him to come home, at least for the summer.

When Matt came home, his parents immediately had him see his pediatrician at Kapiolani Medical Center for Women & Children. She ran a few tests — including blood work — and discovered he had anemia.

And something else.

“She called on a Sunday night and said she had the pathologist go back to the lab and reread the results of the blood test,” Jan said. “That’s not a good thing.”

After even more blood tests and a visit to an oncologist at Straub Clinic & Hospital, Matt was diagnosed with leukemia — two kinds.

He has both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) — extremely rare. So rare, in fact, no one in Hawaii could treat him. So 17 hours after he received this diagnosis, Matt and his parents were on a plane to Seattle.

“We were shocked,” Jan said this afternoon over the phone. “We thought, ‘How could this be?’ Cat, he was healthy. He’s never been sick. We were just stunned.”

I worked for Jan while I was in graduate school at the University of Hawaii at Manoa. She oversaw the marketing department at Title Guaranty, where I had worked part time, and we were instant friends. She was always so much fun, so peppy, so positive. So to hear her now on the phone, exhausted but hopeful, was really hard.

She has been in Seattle since July and doesn’t know when she’s coming back. She took family leave from her job as a fourth grade teacher at Pearl Harbor Kai Elementary School — that lasts a month — and unpaid leave thereafter. Her husband has to return to his job at a boating education specialist with the state Department of Land and Natural Resources soon. They’re spending more than $3,000 a month just on rent in Seattle — and the medical bills are mounting.

This is just the beginning.

This seemingly healthy 20-year-old is now undergoing tiring rounds of chemotherapy, slews of tests and scans, and a roller coaster of emotions. Sometimes he’s fine, laughing with the nurses; other times he’s worn out.

“In these last several weeks, he’s endured so much,” Jan wrote to me in an email last week. “He never complains and has so much inner fortitude. He amazes me.”

Right now, he needs one thing: bone marrow. And there aren’t a lot of matches in the national registry. Turns out, ethnicity matters, and minorities are severely underrepresented in the registry.

Bone marrow is the spongy tissue inside your bones that contain stem cells. The stem cells can develop into red blood cells that carry oxygen through your body, the white blood cells that fight infections and the platelets that help with blood clotting. Leukemia is a cancer in which the bone marrow produces abnormal white blood cells.

Every year 10,000 people need a bone marrow transplant, and only 4 out of 10 will find a match and receive it.

Friends of Matt are holding a bone marrow drive from 1 to 5 p.m. at the Pearl Kai Harbor Elementary School (1 C Avenue, Honolulu). The process is simple: registering only requires donors to swab their cheeks and be ready when they’re called. That’s it.

The more people show up, the better Matt’s chances of finding a match. But it’s not just about him.

“We want to help him, of course, that’s our main goal, but this is a real good way to help others, too,” Jan said.

Learn more about Matt’s story at Caring Bridge. Register — it’s free — and search for “Matthew Inn.”