Doctors at the Children’s Hospital of Philadelphia used zebrafish and a cancer drug to save the life of a boy dying from an overactive lymphatic system.

10-year-old Daniel was a healthy active boy when his body began to swell.

A massive overgrowth of his lymphatic system was overwhelming his major organs.

Hakon Hakonarson, MD, PhD, Director of the Center for Applied Genomics, Children’s Hospital of Philadelphia said, “He had such an overgrowth of the lymphatic vessels that he was leaking fluid into the pericardium, which is the membrane around the heart.”

His lungs suffered too, severely diminishing his oxygen.

“His lung capacity was 23 percent. You know, barely compatible with life,” said Doctor Hakonarson.

Doctors discovered the genetic culprit with a blood test and a simple d-n-a cheek swab. The gene was out of control, meaning daniel’s lymph system was always in the ‘on’ position, Very similar to cancer cells growing out of control. So doctors began to test anti-cancer meds on tiny, translucent zebrafish.

Christoph Seiler, PhD, Research Core Director, Children’s Hospital of Philadelphia said, “The fish develop from a cell to a normal animal in five days.”

“We put this cancer med into the fish, you can’t give them a pill or an injection, so you basically just put it into the water,” said Doctor Hakonarson.

One Melanoma drug called Trametinib, topped the mutation in its tracks. Doctors then gave the drug to daniel.

“His lymphatic system essentially normalized. The child came off oxygen, started walking, started running, started biking and he is essentially with normal daily activities,” said Doctor Hakonarson.

A tiny fish and a very smart team of scientists making a big impact.

Scientists have long used lab rodents or other mammals to help understand human diseases, but 70 percent of human genes are also found in the zebrafish, making them a good animal for study.