Classification of Emphysema

Pulmonary emphysema refers to a  progressive lung disease, it is a form of chronic obstructive pulmonary disease (COPD). Emphysema is mainly a pathological diagnosis which affects the air spaces that are present distal to the terminal bronchiole. It may be characterized by an abnormal permanent enlargement of lung air spaces along with the destruction of their walls without any fibrosis and destruction of lung parenchyma and in loss of elasticity. Emphysema, as a part of COPD, is an illness that mainly affects a large number of people worldwide. In 2016, the Global Burden of Disease Study reported a prevalence of 251 million cases of COPD worldwide. Approximately 90% of COPD deaths occur in low and middle-income countries.

Classification of Emphysema

There are four different types of emphysema, out of which three are related to the anatomy of the lobules of the lung such as the centrilobular or centriacinar, panlobular or panacinar, and paraseptal or distal acinar and are generally not associated with fibrosis (i.e. scarring). However fibrosis is not just a normal feature of these subtypes, repair strategies in end-stage emphysema can also lead to pulmonary fibrosis. The fourth subtype is called the paracicatricial emphysema or irregular emphysema, includes the acinus irregularly and it may be associated with fibrosis.

Mainly the first two types of emphysema – centrilobular, and panlobular are usually associated with a certain amount of airflow obstruction, whereas that of centrilobular emphysema is around 20 times more common than panlobular. The subtypes are visible upon imaging but they are not well-defined clinically. There are also a variety of associated conditions involving bullous emphysema, focal emphysema, and Ritalin lung.

They are discussed as follows:

Centrilobular emphysema 

It is also known as the centriacinar emphysema, it affects the centre of a pulmonary lobule (i.e. centrilobular) present in the lungs, the area around the terminal bronchiole, and the first respiratory bronchiole, and is visible upon imaging as an area around the tip of the visible pulmonary artery. Centrilobular emphysema is a very common type and is usually associated with smoking, and also with chronic bronchitis. The disease progresses generally from the centrilobular portion and leaving the lung parenchyma in the surrounding (i.e. perilobular) region is preserved. Mainly the upper lobes of the lungs are affected.

Panlobular emphysema

Panlobular emphysema is also known as the panacinar emphysema it mainly affects all of the alveoli present in a lobule and usually involves the whole lung or specifically the lower lobes. This type of emphysema is related to alpha-1 antitrypsin deficiency (A1AD or AATD), and Ritalin lung, and is not associated with smoking.

Likely complications of panlobular emphysema, are life-threatening which mainly includes: respiratory failure, pneumonia, respiratory infections, pneumothorax, interstitial emphysema, pulmonary heart disease, and respiratory acidosis.

Paraseptal emphysema: 

Paraseptal emphysema also known as the distal acinar emphysema it is related to some emphysematous change occurring next to a pleural surface, or to a fissure. The cystic spaces are also called as the blebs or bullae that are formed in a paraseptal emphysema it mainly occurs in just one layer below the pleura. This differentiates it from the honeycombing of small cystic spaces as observed in fibrosis that generally occurs in layers. This type of emphysema is not related to any airflow obstruction.

Paracicatricial emphysema

Paracicatricial emphysema, also referred to as irregular emphysema, is visible next to the areas of fibrosis (i.e. scarring) like large spaces. The scarring is most commonly a result of silicosis, granulomatous infection, tuberculosis, or pulmonary infarction. It may be difficult to distinguish it from the honeycombing of pulmonary fibrosis.

Alpha-1 related emphysema

Emphysema is mainly seen to develop in people with alpha-1 antitrypsin deficiency, it is the only genotype of chronic obstructive pulmonary disease. This mainly occurs a lot earlier, as like HIV associated emphysema than other types.

Ritalin lung

The intravenous use of methylphenidate, that is mainly marketed as Ritalin and commonly used as a stimulant drug in the treatment of attention deficit hyperactivity disorder, may lead to emphysematous changes referred to as Ritalin lung. The mechanism underlying this link is not clearly observed. Ritalin tablets comprise talc as a filler, and these are required to be crushed and dissolved for injecting. It has been advised that the talc exposure leads to granulomatosis resulting in alveolar destruction. Although, other intravenous drugs also comprise talc and there is no related emphysematous change observed. High resolution CT scanning displays the emphysema to be panlobular.

Congenital lobar emphysema

Congenital lobar emphysema (CLE), also referred to as the congenital lobar overinflation and infantile lobar emphysema, is mainly a neonatal condition concerned with enlarged air spaces in the lungs of newborn infants. It can be diagnosed at the time of birth or during the first six months of life, it is more common in boys than girls. CLE usually affects the upper lung lobes more than the lower lobes, and the left lung more often than the right lung. CLE can be defined as the hyperinflation of one or more lobes of the lung due to the partial blockage of the bronchus. This leads to symptoms of pressure on the nearby organs. It is mainly associated with several cardiac abnormalities like those of patent ductus arteriosus, atrial septal defect, ventricular septal defect, and tetralogy of Fallot. However, CLE can also be caused via the abnormal development of bronchi, or compression of airways by nearby tissues; no cause can be identified in half of the cases. CT scan of the lungs can be useful in knowing the anatomy of the lung lobes and status of the nearby lobes on whether they are hypoplastic or not. Enhanced CT is very useful in observing vascular abnormalities and mediastinal masses.

Conclusion

Lung volume reduction can be offered to those with advanced emphysema. When other treatments fail, and the emphysema is situated in the upper lobes a surgical option may be also possible. A number of minimally invasive bronchoscopic procedures are widely used to reduce lung volume. So, with this we come to an end of this topic. We hope that you were able to grasp a clear concept of the topic emphysema types.