Diffuse parenchymal lung disease: Clinical

Diffuse parenchymal lung diseases, or DPLDs are a group of rare lung disorders that affect the interstitium of the alveolar wall, the alveoli, as well as the blood vessels and pleura of the lungs.

Previously, they were called interstitial lung diseases because we thought that they only affected the interstitium.

Now, there are literally hundreds of DPLDs out there, so it’s more important to know how to classify them based on their key features than to memorize the names of an ever-growing list of diseases.

DPLDs can be broadly classified into those with a known cause, and those with an unknown cause which are also called idiopathic.

DPLDs that have a known cause can be subclassified into connective tissue diseases, like systemic lupus erythematosus, rheumatoid arthritis, or systemic sclerosis; occupational exposures, like asbestosis, silicosis and berylliosis; granulomatous diseases, like sarcoidosis and hypersensitivity pneumonitis; and treatment-induced causes, like the antiarrhythmic amiodarone, the antibiotic nitrafurantoin, the chemotherapeutic agents methotrexate, bleomycin and busulfan, as well as exposure to radiation.

Now, idiopathic DPLDs include many subtypes, but the most important one is idiopathic pulmonary fibrosis.

In all scenarios, tobacco smoking can potentially worsen an existing DPLD.

Now, DPLDs are classified this way because the known causes are often more treatable and relatively reversible compared to the idiopathic causes.