Lymphangioleiomyomatosis (LAM) is a rare disease mainly affecting women, causing lung damage and breathing problems. This study, called the MIDAS (Multicenter International Durability and Safety of Sirolimus in LAM) Trial, is looking at how safe and effective a drug called sirolimus is for people with LAM. Sirolimus is a type of medicine known as an mTOR inhibitor, which helps to control cell growth. The study is not a treatment trial but will follow 600 LAM patients over at least 2 years to see how their lung function changes and if they have any side effects. It's for adults 18 and older who are on or considering this medicine, or who have tried it before. Researchers want to see if using sirolimus long-term can keep lung problems from getting worse.

• This study lasts at least 2 years.
• Participants will need to attend clinic visits and do lung tests.
• The study is observational, meaning doctors and patients decide on treatment.