The Okayama University Hospital said Wednesday it has succeeded in transplanting parts of a mother's left lung into her 2-year-old son, who became the youngest recipient of a lung transplant in Japan.

It was the world's first lung transplant undertaken after dividing a lung into the smallest possible parts that can function as a lung, the hospital said.

Takahiro Oto, an associate professor in charge of respiratory surgery at the state-run university, said his team operated on the boy, aged 2 years and 9 months, on Aug. 31. An artificial respirator was removed Sept. 13 and he resumed breathing on his own, the surgeon said.

The mother and boy are residents of Saitama Prefecture, north of Tokyo, Mainichi reports.

In late April, the boy suffered from idiopathic interstitial pneumonia which caused his lungs to stop working. He was hospitalized at the Saitama Children's Medical Center in late May.

Medical checks showed that only his mother's lungs would be fit for the boy. His condition worsened due to shortage of oxygen in mid-August. A Self-Defense Forces plane carried the boy to Okayama on Aug. 29.