Lately I've been losing sleep to thoughts of a dead stranger.

I never knew her name or where she lived. I don't know if she liked country music or loved to cook. I have no idea if she had a family.

I do know these three things: She was 59 years old. She had leukemia. And my bone marrow was in her body when she passed.

I donated it to her last November.

It was a match made by science, paired by the National Marrow Donor Program.

I became part of the registry almost a decade ago, when I found out thousands of patients with life-threatening diseases die waiting for bone marrow.

The problem is that a patient needs a donor who is a genetic match. Even with a registry of millions, it's very rare to find a good match.

However, the more people that are in the registry, the better the chances are for getting bone marrow to people in need.

I registered — which requires giving a small vial of blood — knowing I would probably never be called on to actually donate.

And then I got the call.

For the donation, I was anesthetized, then two surgeons inserted what looked like knitting needles into my pelvis, extracting 1.36 liters of marrow.

A cooler full of my marrow was then transported to the dying patient. At that point she'd had enough chemotherapy to kill off her own stem cells, making her ready to accept mine.

I nicknamed her Alice, and I thought of her constantly.

I realize she was very sick and this procedure was her last chance. But somehow I thought my marrow would be enough. I thought I could save her.

Instead, she died about a month after my surgery, I learned just a couple weeks ago.

There aren't words powerful enough to describe how I felt when I received the bad news.

We are forever bonded, Alice and me. We shared the same tissue type. We were a genetic match. Beyond everything superficial and external, we were the same.

I still don't know anything about Alice.

I don't know if she enjoyed romantic comedies or lost herself in science fiction novels. I don't know if she liked to garden or if she had any pets. I don't know if she spent her last days surrounded by friends, relatives and love.

I do know this: Alice died knowing, with all certainty, that someone wanted her to live.

And I know I would do it all over again.

For more information about the National Marrow Donor Program, visit www.marrow.org.