Tokyo - Japan's swim queen Rikako Ikee, a poster girl for next year's Tokyo Olympics, has been diagnosed with leukaemia, the 18-year-old tweeted on Tuesday.
In a shock announcement, Ikee said: "After feeling unwell I returned in haste from Australia and following tests I was diagnosed with leukaemia. I still can't believe it myself and I'm in a state of confusion."
Ikee shot to fame at last year's Asian Games, where she captured a record six gold medals to fire a warning for the 2020 Olympics in her home city.
The teenage superstar, who holds a string of national records, has been tipped to push for gold on several fronts, in particular in the women's 100 metres butterfly.
Ikee told fans she was determined to beat her illness after being forced to abandon her training camp in Australia.
"If treated properly it's a disease that can be beaten," said Ikee, who confirmed she will withdraw from the Japanese championships in April.
"I will devote myself to my treatment and strive to be able to show an even stronger Rikako Ikee."
Ikee stole the headlines from giant Chinese swimmer Sun Yang at the Asian Games in Jakarta as she finished with eight medals in total, a haul previously achieved only by North Korean shooter So Gin Man in 1982.
She would have gone into this year's world championships in South Korea as a strong favourite in the 100m fly, while also a threat in the 200m freestyle.
After her breakout performance in Jakarta, Ikee told AFP in an interview that she welcomed the pressure to produce at the Tokyo Olympics.
"Pressure for me is something I thrive on," she said.
"There will be a lot of Japanese fans cheering for me at the Tokyo Olympics in my home city - maybe even some from overseas too - and that's going to give me great strength."
"The more fans that come, the stronger I'll be," added Ikee.
"When it comes to swimming, I just really hate to lose."
Japanese swimming officials were scheduled to hold a news conference later on Tuesday.