There is no cure but symptoms can be relieved through medication, therapy and lifestyle changes.The singer has opened up about her experience with the illness for the first time in her upcoming documentary.
Below are some celebrities who have publicly spoken about their chronic health conditions: This condition causes pain all over the body and someone suffering with it may also experience extreme tiredness, muscle stiffness, trouble concentrating and problems sleeping.
According to the NHS, it tends to affect women seven times more than men.
Take Lady Gaga, for example, who recently disclosed she has a condition called fibromyalgia.
While it is up to the person in the public eye what they disclose about their health, there's no denying that, especially for the lesser-known conditions, having someone talking about it frankly and publicly can raise awareness, lessen stigma and be a supportive force to fans who may be struggling with something.
HIV damages the cells in the immune system meaning it is difficult for someone infected to fight off infections and diseases.
There is currently no cure but medication allows someone with the condition to live a normal and healthy life.
Lena Dunham has been particularly honest about her experience with the condition, which like so many other sufferers, was misdiagnosed for years.
In April, after five surgeries, she said although there is a risk it may return, she is currently free from the disease.
A chronic illness is a long-term medical condition that requires treatment and management over a long period of time, usually years.
Some of them are well known, like arthritis and diabetes, but there are a whole host of others which have been given more attention in recent years because a celebrity has publicly disclosed having it.
Earlier this year, she hit back at people criticising her for losing weight on social media, telling them it was because of her health issues.