Inflammatory conditions

Respiratory bronchiolitis (RB - ILD):

In pathology reports, between 57 and 100% of smokers have bronchiolitic changes, primarily presented in asymptomatic individuals between 30-40 years. Once patients start developing symptoms (cough and bronchorrhea), the syndrome becomes part of the interstitial lung diseases and occurs usually 20 - 30 years later.

The PFT of these patients demonstrates a restrictive pattern and decreased diffusion capacity (DLCO).

Imaging findings include upper lung predominance, bronchiolocentric poorly defined ground glass (GG) nodules and patches, with bronchial thickening caused by ongoing inflammation due to lack of smoking cessation [5-6].

Even in the typical clinical setting of SR ILD, centrilobular nodules are not specific to the disease and can be found in hypersensitivity (HP) and aspiration pneumonitis. Nevertheless, bronchial thickening and upper lung emphysema are more related to RB - ILD. (Figure 2.)

Desquamative interstitial pneumonia:

Caused by an alveolar occupation of macrophages without the actual desquamation of the epithelial cells and its association with tobacco consumption goes as high as 90%. It presents in individuals between 50 -70 years old. Some predisposing factors have been identified, one of the most relevant are autoimmune diseases in which NSIP pattern is a common presentation, without being part of DIP.

The PFT of these patients demonstrates a restrictive pattern and a marked decrease in DLCO.

HRCT findings include ground-glass opacities (GGO) with symmetrical and bilateral distribution, peripheral and subpleural compromise and conspicuous to the lower lobes. There is no bronchiolocentric distribution. An additional and distinctive finding is the presence of microcysts over the GGO zones. Septal thickening can be also found [3-6]. (Figure 3).

Pneumocystis Jirovecii pneumonia is the principal differential diagnosis, especially in young immunocompromised patients (Figure 4 and 5).

Pulmonary Langerhans Cell Histiocytosis:

Caused by infiltration of the monoclonal proliferation of Langerhans cells. In 85% of patients, the disease compromises the lungs although extrapulmonary manifestations are also encountered, including bone, hypophyseal, lymphatic and visceral infiltration. The relationship with smoking is as high as 90%. Classically a higher prevalence in males was described but with the increasing number of female smokers those trends have gotten closer.

Respiratory and constitutional symptoms are common and PFT varies according to the extension of the disease. 

HRCT findings include nodular bronchiolocentric cystic changes in the upper and middle lung zones with sparing of costophrenic angles. Nodular changes are a cascade of pathologic degeneration of the parenchyma the appearance of various stages of these changes is highly suggestive of PLCH  (figures 6 and 7). Another important feature is the presence of mediastinal lymphadenopathies. Some of the differential diagnoses include infectious conditions, chronic tuberculous changes, chronic hypersensitivity pneumonitis, and cystic metastasis. (Figure 8).

Smoking associated fibrosis:

It is known by pathologic studies that smoking causes fibrotic changes in the lung even without the clinical presentation of idiopathic interstitial pneumonias, but some patterns are specially related to cigarette consumption.

Idiopathic pulmonary fibrosis:

It is the most severe form of chronic idiopathic interstitial pneumonia with usual interstitial pneumonia (USIP) pattern in the histological analysis.

It carries the worst prognosis with median survival rates of only 2.5-3.5 years, being lower in smokers, a fact associated with other lung conditions and atherosclerotic changes.

Typically presents in individuals around 60 years of age with worsening dyspnea, cough, and PFT that demonstrate a restrictive pattern and decreased DLCO.

HRCT findings are divided according to the 2018 ATS guidelines, but typical pattern criteria include reticular opacities, honeycombing, apex-base gradient with the peripheral and subpleural distribution. Traction bronchiectases are a result of the fibrotic changes and there is an absence of GGOs [8]. (Figure 9).

Due to the bad prognosis of the disease and the lack of real impact on survival by antifibrotic therapy, other conditions like coronary and aortic atherosclerosis, cardiomegaly, emphysema, presence of a tumor or other findings take special relevance for the clinician and therefore should be emphasized in the report. (Figure 10).

Combined pulmonary fibrosis and emphysema

It has been recently described that CPFE is a sole entity and not just the superimposition of emphysema and fibrotic changes, being much more common in men and usually in older individuals than IPF. 

Clinical symptoms are the same as in the other conditions and PFT could be normal although DLCO is always decreased.

An important finding in recent studies is the elevated lung cancer risk compared with other conditions, that being said it is imperative to perform a precise identification of suspicious nodules.

Patients present an elevated risk of developing pulmonary hypertension, pulmonary artery diameter can be a helpful finding to include in the report.

HRCT findings include upper lobes emphysema, both centriacinar and paraseptal, and basal reticular opacities, honeycombing, and traction bronchiectases with preservation of lung volumes. (Figure 11).

A dominant pattern of NSIP can also be seen, meaning GGOs do not rule out the diagnosis, as a fact, new studies have found a fibrotic pattern of NSIP associated with smoking but always related to CPFE. The radiologist should report the predominant pattern because it implies a different prognosis [7].

Acute conditions related to cigarette consumption:

Cigarette contains thousands of unidentified substances and antigens,  that can cause hypersensitivity reactions and acute eosinophilic pneumonia. Augmented consumption causes capillaritis, producing diffuse alveolar hemorrhage. Although rare, in the absence of other known precipitating factors recent augmented tobacco consumption should be interrogated [6].