Chest – ILD

“NSIP is less common than UIP. Symptoms of NSIP are similar to those of IPF but usually milder.”

“Treatment of patients with NSIP is based on the use of systemic corticosteroids in combination with cytotoxic drugs, such as cyclophosphamide and cyclosporin, and the majority of patients stabilize or improve with this therapy.”

“The most common manifestation consists of patchy ground-glass opacities combined with irregular linear or reticular opacities and scattered micronodules. In advanced disease, traction bronchiectasis and consolidation can be seen. Ground-glass opacities remain the most obvious high-resolution CT feature in the typical patient with NSIP.“

“Other findings in advanced NSIP include subpleural cysts, but compared to those of UIP, these cysts are smaller and limited in extent. The term “microcystic honeycombing” is used for these cystic changes in NSIP, as opposed to the macrocystic honeycombing seen in UIP. Although the CT features of cellular and fibrotic NSIP overlap considerably, it has been shown that honeycombing is seen almost exclusively in patients with fibrotic NSIP. Other CT findings that have been correlated with increased likelihood of fibrosis in NSIP are the extent of traction bronchiectasis and intralobular reticular opacities.”

“The histologic pattern of COP is organizing pneumonia, formerly referred to as bronchiolitis obliterans organizing pneumonia (BOOP). The term BOOP has been omitted to avoid confusion with airway diseases such as constrictive bronchiolitis. The majority of patients recover completely after administration of corticosteroids, but relapses occur frequently within 3 months after corticosteroid therapy is reduced or stopped.”

“The histologic hallmark of organizing pneumonia is the presence of granulation tissue polyps in the alveolar ducts and alveoli. The lung abnormalities show a characteristic peripheral or peribronchial distribution, and the lower lung lobes are more frequently involved. In some cases, the outermost subpleural area is spared. Typically, the appearance of the lung opacities varies from ground glass to consolidation.”

“RB-ILD is a smoking-related interstitial lung disease and is thought to represent an exaggerated and symptomatic form of the histologically common and incidental finding of respiratory bronchiolitis. Because of the significant overlap in clinical, imaging, and histologic features between RB-ILD and DIP, these entities are considered a pathomorphologic continuum, representing different degrees of severity of the same disease process.”

“Smoking cessation is the most important component in the therapeutic management of RB-ILD. However, the majority of patients also receive corticosteroid therapy.”

“RB-ILD has an upper lung predominance. The key high-resolution CT features of RB-ILD are centrilobular nodules in combination with ground-glass opacities and bronchial wall thickening. Coexisting moderate centrilobular emphysema is common, given that most patients have a smoking history.”

“DIP is strongly associated with cigarette smoking and is considered to represent the end of a spectrum of RB-ILD. However, DIP also occurs in nonsmokers and has been related to a variety of conditions, including lung infections and exposure to organic dust.”

“At high-resolution CT, DIP is characterized by diffuse ground-glass opacities, which correlate histologically with the spatially homogeneous intraalveolar accumulation of macrophages and thickening of alveolar septa. Usually, there is a peripheral and lower lung lobe predominance. Other frequent CT findings include spatially limited irregular linear opacities and small cystic spaces, which are indicative of fibrotic changes.”

“Despite differences in the CT appearance of RB-ILD and DIP, imaging findings may overlap and may be indistinguishable from each other. To improve diagnostic accuracy, lung biopsy is required in all cases of suspected RB-ILD or DIP.”

“LIP is exceedingly rare. It is far more common as a secondary disease in association with systemic disorders, most notably Sjögren syndrome, human immunodeficiency virus infection, and variable immunodeficiency syndromes. Corticosteroids are used in the therapy of LIP, but response is unpredictable and no controlled randomized treatment trials have been reported to date.”

“The dominant high-resolution CT feature in patients with LIP is ground-glass attenuation, which is related to the histologic evidence of diffuse interstitial inflammation. Another frequent finding is thin-walled perivascular cysts. In contrast to the subpleural, lower lung cystic changes in UIP, the cysts of LIP are usually within the lung parenchyma throughout the mid lung zones and presumably result from air trapping due to peribronchiolar cellular infiltration. In combination with ground-glass opacities, these cysts are highly suggestive of LIP. Occasionally, centrilobular nodules and septal thickening are seen.”

“AIP is the only entity among the IIPs with acute onset of symptoms. In most cases of AIP, the clinical and imaging criteria for acute respiratory distress syndrome are fulfilled. Most patients develop severe dyspnea with a need for mechanical ventilation within less than 3 weeks.”

“The histologic pattern of AIP includes diffuse alveolar damage, which can be categorized into an early exudative phase and a chronic organizing phase.” Acute phase = exudative phase, chronic phase = fibrotic phase.

AIP: “The costophrenic angles are often spared. In the early phase of AIP, ground-glass opacities are the dominant CT pattern and reflect the presence of alveolar septal edema and hyaline membranes. Areas of consolidation are also present but are usually less extensive and limited to the dependent area of the lung. In the early phase, airspace consolidation results from intraalveolar edema and hemorrhage.”

“Consolidations are also present in the fibrotic phase and then result from intraalveolar fibrosis. In the late phase of AIP, architectural distortion, traction bronchiectasis, and honeycombing are the most striking CT features and are more severe in the nondependent areas of the lung.”

“The ‘crazy-paving’ pattern at thin-section computed tomography (CT) of the lungs is characterized by scattered or diffuse ground-glass attenuation with superimposed interlobular septal thickening and intralobular lines.”

Pulmonary alveolar proteinosis: “Dyspnea and nonproductive cough are the most common associated symptoms, whereas pleuritic chest pain, malaise, and low-grade fever are less common. The diagnosis is established with bronchoalveolar lavage.”

“Organizing pneumonia, also known in the past as bronchiolitis obliterans organizing pneumonia, is a chronic inflammatory process characterized by focal plugs of granulation tissue (Masson bodies) in the lumina of distal small airways, often extending into the alveolar spaces, associated with intraalveolar foamy macrophages and an interstitial cellular response. Most cases of organizing pneumonia are idiopathic (cryptogenic organizing pneumonia). An association with collagen-vascular diseases (rheumatoid arthritis, mixed connective-tissue disease), infection, and toxic effects of drugs (bleomycin, methotrexate, cyclophosphamide, gold salts, topotecan, amiodarone) has been reported. Patients usually present with cough, dyspnea, fever of several weeks duration, and leukocytosis. Response to steroid therapy is typical.”

“Exogenous lipoid pneumonia is a pulmonary disorder resulting from chronic aspiration or inhalation of animal, vegetable, or petroleum-based oils or fats. Predisposing factors such as structural abnormalities of the pharynx, esophageal disorders (achalasia, Zenker diverticulum, hiatus hernia, and reflux), neurologic defects, and chronic illness are common. However, in many cases, no predisposing condition is found.”

“Adult respiratory distress syndrome is a form of pulmonary edema characterized by refractory hypoxemia and respiratory distress. Numerous causes have been reported, including shock, contusion, infection, sepsis, aspiration, drug abuse, and inhalation of noxious substances.”

“Pulmonary hemorrhage syndromes include a wide spectrum of diseases, including idiopathic pulmonary hemosiderosis, Wegener granulomatosis, Churg-Strauss syndrome, Goodpasture syndrome, collagen-vascular disease (systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, polymyositis, and mixed connective-tissue disease), drug-induced coagulopathy, and hemorrhage associated with malignancy.”

Causes of the crazy-paving pattern:
Infection: Pneumocystis carinii pneumonia (PCP)
Neoplasm: Mucinous bronchioalveolar carcinoma (BAC)
Idiopathic: Pulmonary alveolar proteinosis (PAP), sarcoidosis, nonspecific interstitial pneumonia (NSIP), organizing pneumonia (OP)
Inhalation: Lipoid pneumonia
Sanguineous: Adult respiratory distress syndrome (ARDS), pulmonary hemorrhage syndromes