Kyoto University Hospital said Monday that it has performed the world's first simultaneous lung and liver transplant from living donors.

In the operation on Nov. 15 last year, a boy under the age of 10 with a genetic disorder received part of his parents' lungs and part of his grandfather's liver.

The boy, from the Kanto region, is recovering well after the operation. He was able to walk without an oxygen tank two and a half months later, and he left the hospital and returned to his home on Friday. His parents and grandfather have also returned to socializing.

There have been cases of simultaneous lung and liver transplants from brain-dead donors overseas, but no such cases in Japan due to a lack of such donors, according to the university hospital.

"We were able to open up a new therapeutic option for patients," said Hiroshi Date, a professor at the university hospital who performed the operation.

The boy who underwent the operation had been diagnosed with dyskeratosis congenita. He developed aplastic anemia at the age of 2 and received a bone marrow transplant from his sister at the age of 4.

He later developed liver cirrhosis and a condition in which the arteries and veins of his lungs were connected, making him unable to take in oxygen. He therefore needed both lung and liver transplants.