What is Diffuse Parenchymal Lung Disease?
Diffuse parenchymal lung disease is one of several restrictive lung diseases. Alternate names for this disease include: diffuse interstitial lung disease, alveolitis, cryptogenic fibrosing alveolitis (CFA), and idiopathic pulmonary pneumonitis (IPP).
These are all conditions where the deep, inner tissues of the lungs become inflamed. Some of the membranes in between the alveoli and bronchi are so thin they can't even be observed under a microscope. But just like more visible structures, these membranes and tissues can also become inflamed and infected - and consequently affect normal breathing patterns.
When a person's total lung capacity (TLC), vital capacity, or resting lung volume is reduced that person is said to have a restrictive lung disease and investigation will begin into which specific condition is present. Parenchymal lung disease is also characterized by reduced gas transfer.
Restrictive lung diseases are divided into two groups according to the anatomical structures that they affect: intrinsic and extrinsic. Intrinsic lung diseases refer to diseases that cause inflammation or scarring of the lung tissue or fill the alveoli with exudate and debris (pneumonitis). Other such diseases include: idiopathic fibrotic diseases, connective-tissue diseases, drug-induced lung disease, and other primary lung diseases (including sarcoidosis). Extrinsic disorders affect the chest wall, pleura, and respiratory muscles.
In the early stages of these interstitial lung diseases, white blood cells, macrophages, and protein-rich fluid accumulate in the interstitial spaces (alveoli and the spaces around blood vessels and small airways), and cause inflammation. As the alveoli are destroyed, thick-walled cysts are left behind leaving the lungs to resemble a honeycomb and leading to an eventual diagnosis of pulmonary fibrosis.
Symptoms and Diagnosis
Normally, air flows in and out of the alveoli, causing the lungs to inflate and deflate with each cycle. Lung inflation does not only involve the lungs, but the working of many surroundings muscles, as well.