Canadian pop singer Justin Bieber has revealed he has been diagnosed with Lyme disease.
"It's been a rough couple years," adding that he was also suffering from a chronic viral infection.
The star said he was aware of social media speculation that he had a drug problem, after he was pictured looking unwell with blotches on his skin.
Lyme disease is caused by bacteria carried by some species of ticks.
Symptoms of the infection often include a rash, muscle pain, and tiredness.
What did Bieber say?
On his Instagram page, the artist wrote that people had suggested he looked like he was "on meth", but "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".
He said he was getting "the right treatment" to help address the disease, and that more would be revealed in an upcoming YouTube documentary series about his life.
"You can learn all that I've been battling and OVERCOMING!!" he wrote, telling his 124 million Instagram followers: "I will be back and better than ever".
The superstar's wife, model Hailey Bieber, defended her husband against criticism from those "trying to downplay the severity of Lyme disease".
"Please do your research," she urged them on Twitter on Wednesday.
End of Twitter post by @haileybieber
Morven-May MacCallum is still suffering nine years after starting treatment
What is Lyme disease?
Lyme disease - a bacterial infection - is carried by some species of ticks, and about 13% in the UK are believed to be infected
It cannot be passed on from person to person
Symptoms - including the bulls-eye rash, fatigue and fever - usually develop around three weeks after a bite
The majority of those who take the full three-week course of antibiotics make a full recovery
The New Forest and the Scottish Highlands are known Lyme disease hotspots - but people should take care wherever there is long grass
The NHS test, which is highly accurate, looks at antibodies the body produces, which can take some weeks to reach detectable levels
Source: Public Health England/NHS