Diffuse panbronchiolitis (DPB) is an inflammatory lung disease of unknown cause. It is a severe, progressive form of bronchiolitis, an inflammatory condition of the bronchioles (small air passages in the lungs). The term diffuse signifies that lesions appear throughout both lungs, while panbronchiolitis refers to inflammation found in all layers of the respiratory bronchioles (those involved in gas exchange). DPB causes severe inflammation and nodule-like lesions of terminal bronchioles, chronic sinusitis, and intense coughing with large amounts of sputum production. The disease is believed to occur when there is susceptibility, or a lack of immune system resistance, to DPB-causing bacteria or viruses, caused by several genes that are found predominantly in individuals of East Asian descent. The highest incidence occurs among Japanese people, followed by Koreans. DPB occurs more often in males and usually begins around age 40. It was recognized as a distinct new disease in the early 1960s and was formally named diffuse panbronchiolitis in 1969. If left untreated, DPB progresses to bronchiectasis, an irreversible lung condition that involves enlargement of the bronchioles, and pooling of mucus in the bronchiolar passages. Daily treatment of DPB with macrolide antibiotics such as erythromycin eases symptoms and increases survival time, but the disease currently has no known cure. The eventual result of DPB can be respiratory failure and heart problems. Classification
The term "bronchiolitis" generally refers to inflammation of the bronchioles. DPB is classified as a form of "primary bronchiolitis", which means that the underlying cause of bronchiolitis is originating from or is confined to the bronchioles.
In free fatty acid form, the chemical structure of stearidonic acid is:

Examples
Polyunsaturated fatty acids with 16- and 18-carbon chains are sometimes classified as short chain polyunsaturated fatty acids (SC-PUFA), as opposed to long-chain polyunsaturated fatty acids (LC-PUFA), which have more than 18 carbon atoms.Both the essential fatty acids are SC-PUFA with an 18-carbon chain:

ω-3 fatty acid:
α-linolenic acid or ALA (18:3n-3)
ω-6 fatty acid:
linoleic acid or LA (18:2n-6)These two fatty acids cannot be synthesized by humans because humans lack the desaturase enzymes required for their production. They form the starting point for the creation of more desaturated fatty acids, most of which also have a longer carbon chain:

ω-3 fatty acids:
eicosapentaenoic acid or EPA (20:5n-3)
docosahexaenoic acid or DHA (22:6n-3)
ω-6 fatty acids:
gamma-linolenic acid or GLA (18:3n-6)
dihomo-gamma-linolenic acid or DGLA (20:3n-6)
arachidonic acid or AA (20:4n-6)Except for GLA, which has a short 18-carbon chain, these fatty acids have more than 18 carbon atoms and are typically classified as LC-PUFA.ω-9 fatty acids are not essential in humans because they can be synthesized from carbohydrates or other fatty acids. Essentiality in human diet
Mammals lack the ability to introduce double bonds in fatty acids beyond carbon 9 and 10, hence the omega-6 linoleic acid (18:2n-6; LA) and the omega-3 Alpha-linolenic acid (18:3n-3; ALA) are essential for humans in the diet. However, humans can convert both LA and ALA to fatty acids with longer carbon chains and a larger number of double bonds, by alternative desaturation and chain elongation. In humans, arachidonic acid (20:4n-6; AA) can be synthesized from LA.