Aplastic anemia was once a disease that terrified doctors, mysteriously shutting down the bone marrow’s ability to make blood cells and threatening the young and healthy with death. But in the the late 1970s, hematologist Neal S. Young saw the disease as one that held not only fear but also potential for his field.

“It was a horrific and intriguing disease: untreatable, often afflicting the young, but so mysterious that there was a possibility of getting patients better immediately,” he said — if only the mystery could be solved.

Young, just starting as a physician-scientist at the National Institutes of Health, found the cure. It was the first in a prolific chain of discoveries for which he has been nominated for a Samuel J. Heyman Service to America award.

Young, a finalist for the Science and Environment medal, is one of 33 federal employees nominated in nine categories who will be honored for outstanding service to advance the nation’s health and safety on Thursday, when winners will be announced.

Now the chief of the hematology branch at NIH’s National Heart, Lung, and Blood Institute, he is regarded as a world expert on bone-marrow-failure diseases. His Bethesda clinic draws young and old from around the world who cannot make the blood cells they need to survive. He is also a director of NIH’s Center for Human Immunology, Autoimmunity and Inflammation, and trains hematologists around the world.

Dr. Neal Young. (Photo by Ernie Branson/NIH)

Young recalled that the fear surrounding aplastic anemia when he was a medical resident in the 1970s was overwhelming.

“There was a terrifying sense of drama,” he said. “Perfectly healthy people started bleeding, becoming anemic and succumbing to awful infections.”

That’s because their bone marrow had stopped making platelet cells that help the blood clot, as well as red blood cells that carry oxygen and white blood cells that fight infection. The anemia is rare, striking from 600 to 900 people in the United States and a few thousand around the world each year.

The scariest part in those days, Young added, was looking at the samples of his anemic patients’ bone marrow. “It would be totally empty of blood cells — it was just yellow fat.”

Nobody knew how one acquired aplastic anemia, or who was at risk. Some doctors thought it could be contracted by coming into contact with a bad chemical or drug. Others speculated that it was an autoimmune disease; the body attacking its own bone marrow like it would a bacteria or a virus.

But that idea had never been proved, and in the early 1980s Young conducted the first nationwide clinical trial to test if a treatment that suppressed the immune system could cure the anemia and allow the bone marrow to regenerate.

“I had just begun my career — when I look back now, I can’t believe I had the gumption to try and organize such a huge study,” he said.

The trial included roughly 150 aplastic anemia patients at 12 clinical sites around the country. More than half of the patients who received immunosuppressive treatment improved.

“The idea that you would treat the immune system for the anemia was novel. . . . It was a scientific insight with immediate repercussions,” Young said.

Immunosuppressive therapy is now standard worldwide. The recovery rate is more than 70 percent. The previous recovery rate for aplastic anemia was 10 percent.

One patient in that 70 percent is Jordan Culbreath, 24, a Falls Church native. Voted captain of Princeton University’s football team and the 2009 preseason pick for Ivy League offensive player of the year, Culbreath’s senior year held great promise. But he struggled in summer training camp: His bruises weren’t healing, his limbs were numb and he bled easily. After receiving a diagnosis of aplastic anemia and lacking a match for a bone marrow transplant, he found his way to Young by the middle of football season.

“Dr. Young has this incredible confidence in your ability to recover,” he said. At one point during his illness, Culbreath feared he would never play football again. It was Young, he said, who got him back on the field for the following season.

Culbreath graduated in 2011 with a degree in mechanical and aerospace engineering.

Stories of recovery, Young said, are now more frequent than ever.

“At the beginning, there were so many patients dying in our wards that getting just one person better was a big deal,” he said. “Now it’s the reverse. When one of our patients dies, it’s a really big deal because most of them are able to live long.

Young grew up in Flushing, N.Y., and graduated cum laude from Harvard in 1967 and Johns Hopkins University School of Medicine in 1971. At Harvard, he was the singles sculling champion and remains a competitive masters sculler. This fall, in Rio de Janeiro, he will complete a personal quest to row on every continent. He is married to Genoveffa Franchini, a virologist and hematologist at the National Cancer Institute who specializes in HIV research. They have three sons, all of whom attended Sidwell Friends School.

Arthur Nienhuis, a leading hematologist at St. Jude Children’s Research Hospital, was the NIH’s chief of hematology when Young began aplastic anemia research. Offering Young a permanent position in 1981, Nienhuis said, was “a natural choice.”

“He was extraordinarily gifted, with a genuine interest in disease treatment,” he said. “The decision to hire him is one I remain quite proud of.”

Since Young’s landmark 1988 clinical trial for aplastic anemia, he has continued to push the boundaries of bone-marrow-failure research. In the 1990s, he discovered that a highly contagious virus called parvovirus B19 halts red blood cell production. Young, who says parvovirus B19 is now one of the best understood human viruses, has discovered ways to diagnose and treat the infection, and he is leading the development of a vaccine.

His latest line of research is studying the link between bone marrow diseases and faulty maintenance of telomeres, which are bits of DNA that protect the ends of our chromosomes from dangerous wear and tear.

Young said that NIH has given him a rare amount of intellectual freedom inside the laboratory.

“They let me follow my nose from dead end to dead end until I stumble upon something promising,” he said.

“But there’s nothing as concrete as being able to treat a really sick patient and get them better,” he added. “That’s why I do this.”