..is a collapsed lung dangerous

[mum2sam]

and how can it be treated? A family member has just been diagnosed with this.

not dangerous as far as I know. Just very painful - I was given loads of painkillers and it evenutally sorted itself out.

jsut looked online and there are lots of different types, and it depends on the severity. Mine was caused by a twin pregnancy so I guess not so bad.

Usually a pneumothorax is treated according to size. Small ones can respond to rest and painrelief and the body will sort it out given time, larger ones need a chest drain to be inserted to allow the air to escape from where it has become trapped between the lung and chest wall.
A tension pneumothorax is much more dangerous as the pressure around the collapsed lung builds up and eventually shunts everything across and compresses the good lung and heart, so not a good thing to have at all, but again it is readily treated with a chest drain.
Some people, usually tall, slender teenagers and those in their 20's, seem to be more prone to this happening spontaneously. Otherwise it can be associated with chest / rib trauma or certain lung diseases. It can also occur following very hard laughing - so no trips to see live comedy