There are four main types of emphysema, three of which are related to the anatomy of the
lobules of the lung – centrilobular or centriacinar, panlobular or panacinar, and paraseptal or distal acinar and are not associated with
fibrosis (scarring). Although fibrosis is not a normal feature of these subtypes, repair strategies in end-stage emphysema may lead to
pulmonary fibrosis. Usually the upper lobes of the lungs are affected. The upper lobes of the lungs are more susceptible to centrilobular emphysema because of their higher ventilation:perfusion ratio due to gravity. The apices of the lungs have less particle filtration because of lower blood and lymphatic flow compared to the bases of the lungs.
Panlobular Panlobular emphysema, also called
panacinar emphysema, affects all of the alveoli in a lobule, and can involve the whole lung or mainly the lower lobes. This type of emphysema is associated with
alpha-1 antitrypsin deficiency (A1AD or AATD), and
Ritalin lung,
Paraseptal Paraseptal emphysema, also called
distal acinar emphysema, relates to emphysematous change next to a
pleural surface, or to a
fissure. The cystic spaces known as
blebs or bullae that form in paraseptal emphysema typically occur in just one layer beneath the pleura. This distinguishes it from the
honeycombing of small cystic spaces seen in
fibrosis that typically occurs in layers.
Bullous When the
subpleural bullae are significant, the emphysema is called
bullous emphysema. Bullae can become extensive and combine to form giant bullae. These can be large enough to take up a third of a hemithorax, compress the lung parenchyma, and cause displacement. The emphysema is now termed
giant bullous emphysema, more commonly called
vanishing lung syndrome due to the compressed parenchyma. A
bleb or bulla may sometimes rupture and cause a
pneumothorax.
Paracicatricial Paracicatricial emphysema, also known as irregular emphysema, is seen next to areas of
fibrosis (scarring) as large spaces. The scarring is most often a result of
silicosis,
granulomatous infection,
tuberculosis, or
pulmonary infarction. It can be difficult to differentiate from the
honeycombing of
pulmonary fibrosis.
HIV associated Classic lung diseases are a complication of
HIV/AIDS with emphysema being a source of disease. HIV is cited as a risk factor for the development of emphysema and COPD regardless of smoking status. Around 20 percent of those with HIV have increased emphysematous changes. This has suggested that an underlying mechanism related to HIV is a contributory factor in the development of emphysema. HIV associated emphysema occurs over a much shorter time than that associated with smoking; an earlier presentation is also seen in emphysema caused by
alpha-1 antitrypsin deficiency. Both of these conditions predominantly show damage in the lower lungs, which suggests a similarity between the two mechanisms.
Alpha-1 related Emphysema may develop in some people with
alpha-1 antitrypsin deficiency, the only
genotype of chronic obstructive pulmonary disease. This usually occurs a lot earlier (as does HIV associated emphysema) than other types.
Ritalin lung The intravenous use of
methylphenidate, commonly marketed as
Ritalin and widely used as a
stimulant drug in the treatment of
attention deficit hyperactivity disorder, can lead to emphysematous changes known as
Ritalin lung. The mechanism underlying this link is not clearly understood. Ritalin tablets are not intended to be injected. They contain
talc as a filler, and it has been suggested that talc exposure causes
granulomatosis leading to alveolar destruction. However, other intravenous drugs also contain talc, and no emphysematous change is associated with those.
High resolution CT scanning shows the emphysema to be panlobular.
CPFE Combined pulmonary fibrosis and emphysema (CPFE) is a rare syndrome that shows upper-lobe emphysema, together with lower-lobe interstitial fibrosis. This is diagnosed by
CT scan. This syndrome presents a marked susceptibility for the development of
pulmonary hypertension.
SRIF Smoking-related interstitial fibrosis (SRIF) is another type of fibrosis that occurs in emphysematous lungs and can be identified by pathologists. Unlike CPFE, this type of fibrosis is usually clinically occult (i.e., does not cause symptoms or imaging abnormalities). Occasionally, however, some patients with SRIF present with symptoms and radiologic findings of interstitial lung disease.
Congenital lobar Congenital lobar emphysema (CLE), also known as congenital lobar overinflation and infantile lobar emphysema, is a
neonatal condition associated with enlarged air spaces in the lungs of
newborn infants. It is diagnosed around the time of birth or in the first 6 months of life, occurring more often in boys than girls. CLE affects the upper
lung lobes more than the lower lobes, and the left lung more often than the right lung. Although CLE may be caused by the abnormal development of
bronchi, or compression of airways by nearby tissues, no cause is identified in half of cases. CT scan of the lungs is useful in assessing the anatomy of the lung lobes and status of the neighbouring lobes on whether they are hypoplastic or not. Contrast-enhanced CT is useful in assessing vascular abnormalities and mediastinal masses. This is also known as
localized pulmonary emphysema.
Blebs and bullae may also be included as focal emphysema. These can be differentiated from the other type of enclosed air space known as a
lung cyst by their size and wall thickness. A bleb or bulla has a wall thickness of less than 1 mm, and are smaller.
Occupational A number of occupations are associated with the development of emphysema due to the inhalation of varied gases and particles. In the US
uranium mining that releases
radon gas and particles has been shown to be a cause of emphysema deaths; the figures in the study included some miners who also smoked. Uranium mining and milling was found to create environmental pollution. The inhalation of
coal mine dust that can result in
coalworker's pneumoconiosis is an independent risk factor for the development of emphysema. Focal emphysema is associated with the
coal macule, and this extends into progressive centrilobular emphysema. Less commonly a variant of panlobular emphysema develops.
Silicosis results from the inhalation of
silica particles, and the formation of large silica nodules is associated with paracicatricial emphysema, with or without bullae.
Ozone-induced emphysema Ozone is another
pollutant that can affect the respiratory system. Long-term exposure to ozone can result in emphysema. ==Osteoporosis==