Zebrafish to The Rescue!


PHILADELPHIA, Pa. (Ivanhoe Newswire) — Lymphatic systems help clear the body of extra fluids and infection, but when they don’t work properly, deadly excess fluid is retained in the body. That was the case with a young boy whose family sought help at Children’s Hospital of Philadelphia. By testing various medications using tiny zebrafish, doctors miraculously saved his life.

Ten-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.

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

(Read Full Interview)

His lungs suffered too, severely diminishing his oxygen.

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

Doctors discovered the genetic culprit with a blood test and a simple DNA 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 at 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,” stated Dr. Hakonarson.

One melanoma drug called trametinib, stopped 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,” Dr. Hakonarson told Ivanhoe.

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.

Contributors to this news report include: Cyndy McGrath, Supervising Producer; Donna Parker, Field Producer; Roque Correa, Videographer and Editor.

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REPORT:       MB #4658

BACKGROUND: The lymphatic system is a vital part of the immune system, along with the thymus, bone marrow, spleen, tonsils, appendix, and Peyer’s patches in the small intestine. Like the venous system, the lymphatic system transports fluids throughout the body. The lymphatic system consists of thin-walled lymphatic vessels, lymph nodes, and two collecting ducts. Disorders of the lymphatic system may occur because of blockage, infection, or cancer. Tumors may block the lymphatic ducts or may travel to lymph nodes near a tumor, interfering with flow of lymphatic fluid through the node. Rarely, a tumor (lymphangiosarcoma) may develop in the lymphatic system.

(Source: https://www.merckmanuals.com/home/heart-and-blood-vessel-disorders/lymphatic-disorders/overview-of-the-lymphatic-system)

INTEREST: Hakon Hakonarson, MD, PhD, Director of Center for Applied Genomics at the Children’s Hospital of Philadelphia talked about how a coworker’s son had a lymphatic condition, “His mother asked me if she would be able to provide some funding, could we work on this condition and try to resolve it? This was probably five or six years ago. And I said, of course, we would be happy to help. And so, we ended up collecting samples from her family. It was actually a four- generation family that we have samples from. And we found a new gene, new mutation.” This sparked the interest in lymphatic conditions, and they started recruiting patients from all over the U.S.

(Source: Hakon Hakonarson, MD, PhD)

SYMPTOMS: Dr. Hakonarson explained the common symptoms of a lymphatic condition, “The central duct is most likely to begin leaking fluid into the chest, but then it goes into the abdomen and into the heart and into the extremities, or there’s gravity so you have more on the lower extremities than you have on the upper. But essentially anywhere in the body because the lymphatic system is all over the body, there’s this sort of fluid leak happening, so patients who have the DMA – they should be checked out to see if they have a lymphatic condition. Sometimes it’s the venous system – varicose veins and problems with the venous system – but sometimes it’s the lymphatic system.”

(Source: Hakon Hakonarson, MD, PhD)


John Ascenzi

Senior Medical and Science Writer



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Doctor Q and A

Read the entire Doctor Q&A for Hakon Hakonarson, MD, PhD, Director of Center for Applied Genomics

Read the entire Q&A