Interstitial lung disease

Interstitial lung disease
Other names	Diffuse parenchymal lung disease (DPLD)
End-stage pulmonary fibrosis of unknown origin, taken from an autopsy
Specialty	Pulmonology
Complications	Respiratory failure
Usual onset	Months – years, depending on cause/type
Duration	Months – years, depending on cause/type
Frequency	1.9 million (2015)[1]
Deaths	122,000 (2015)[2]

Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD),^[3] is a group of respiratory diseases affecting the interstitium (the tissue) and space around the alveoli (air sacs) of the lungs.^[4] It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, and perivascular and perilymphatic tissues. It may occur when an injury to the lungs triggers an abnormal healing response. Ordinarily, the body generates just the right amount of tissue to repair damage, but in interstitial lung disease, the repair process is disrupted, and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into the bloodstream. The disease presents itself with the following symptoms: shortness of breath, nonproductive coughing, fatigue, and weight loss, which tend to develop slowly, over several months. The average rate of survival for someone with this disease is between three and five years.^[5] The term ILD is used to distinguish these diseases from obstructive airways diseases.

There are specific types in children, known as children's interstitial lung diseases. The acronym ChILD is sometimes used for this group of diseases.^[6]

Thirty to 40% of those with interstitial lung disease eventually develop pulmonary fibrosis which has a median survival of 2.5-3.5 years.^[7] Idiopathic pulmonary fibrosis is interstitial lung disease for which no obvious cause can be identified (idiopathic) and is associated with typical findings both radiographic (basal and pleural-based fibrosis with honeycombing) and pathologic (temporally and spatially heterogeneous fibrosis, histopathologic honeycombing, and fibroblastic foci).

In 2015, interstitial lung disease, together with pulmonary sarcoidosis, affected 1.9 million people.^[1] They resulted in 122,000 deaths.^[2]