I just got diagnosed with a very rare lung disease called desquamated interstitial pneumonitis. what is this & how could i have got this & lifespan?

DIP: This is a specific type of lung disease that is indeed rare. A certain kind of cell (macrophage) accumulates in the airspaces of the lungs and can cause inflammation. It is highly associated with cigarette smoking (>90%). If diagnosed fairly early (before scarring/fibrosis develop), the prognosis can be good with treatment , but smoking cessation is critical to a good outcome.

Lung inflammation: Desquamative insterstitial pneumonia is a kind of inflammation of the lung tissue in which many kinds of infection fighting white blood cells invade and injure the lungs especially a kind of WBC called a macrophage. The cause is not known, but most patients are smokers and stopping smoking improves 3/4 of patients. Others benefit from steroid medicine in addition to decrease inflammation.