Interstitial Lung Disease (ILD) comprise a variety of illnesses that damage the lung tissue around the alveoli (“interstitial” means “between cells”). As such, these conditions prevent the lung from expanding well, and interfere with oxygen transferring into the bloodstream. They are “restrictive” lung diseases, as opposed to Asthma and COPD, which are “obstructive” diseases that affect the airway (COPD) (see Diagram — Lower Respiratory Tract).
Many cases of ILD may be complications of other illnesses, like Rheumatoid Arthritis, Sarcoidosis, etc. A type of “allergy” called Hypersensitivity Pneumonitis results in ILD (not a true “allergy” like asthma, but caused by specific environmental irritants). Various medications can cause ILD, including some common ones if an individual is unlucky enough to be predisposed. Finally, there are a number of types of ILD that are “idiopathic,” meaning they just happen on their own, nobody knows why.
ILD causes a dry cough and/or gradual shortness of breath. It’s often misdiagnosed at first as asthma or COPD, but those treatments don’t help at all. Pulmonary function testing easily distinguishes the two. Chest x-rays can show ILD as it becomes more advanced; earlier diagnosis requires a special type of CT scan called “high resolution CT”.
To find the specific cause of ILD, it may be necessary to do a lung biopsy. Treatment consists of medicines that interfere with the immune system. It’s not a cure, though in some cases can help maintain health for a number of years. But depending on the exact sub-type of ILD, in other cases the disease advances rapidly and is ultimately fatal.