Interstitial lung disease is a general term that encompasses a number of chronic lung condiitions. No matter what the condition, though, interstitial lung disease always begins with inflammation, which can have a variety of causes.
The inflammation then affects the interstitum, the tissue between the air sacs in the lungs. The inflammation may go away by itself or it may cause scarring, or fibrosis. When fibrosis occurs, the tissue can no longer carry oxygen and the lung becomes stiff.
Symptoms and progression of the disease varies depending on the amount of scarring.
Your pulmonologist may request a VATS biopsy to obtain lung tissue for diagnosis to determine the precise type of scarring.