Justin Bieber has told fans he has been battling Lyme disease and that he will go into more detail in his upcoming docu-series.
The singer, 25, posted a long message on Instagram saying that he had been diagnosed with the bacterial infection and that it had been "a rough couple of years".
However, he vowed to be "back and better than ever".
Bieber told his 124 million followers on the site: "While a lot of people kept saying Justin Bieber looks like s***, on meth etc they failed to realise I've been recently diagnosed with Lyme disease, not only that but had a serious case of chronic mono which affected my skin, brain function, energy, and overall health.
"These things will be explained further in a docu series I'm putting on YouTube shortly.. you can learn all that I've been battling and OVERCOMING!!"
He added: "It's been a rough couple years but getting the right treatment that will help treat this so far incurable disease and I will be back and better than ever NO CAP."
Bieber revealed last month that he is to star in a documentary series which will give fans a look at the making of his first new album in more than four years.
The YouTube programme will also give fans an insight into the past few years of the singer's life, from his marriage to Hailey Baldwin to his struggles.
Justin Bieber: Seasons will debut on January 27, with new episodes launching each Monday and Wednesday. The 10-episode docu-series will be available free to watch (with ads) on YouTube.
According to the NHS website, Lyme disease is "a bacterial infection that can be spread to humans by infected ticks".
It says a few people who are diagnosed and treated for Lyme disease continue to have symptoms, including "tiredness, aches and loss of energy".