Desquamative Interstitial Pneumonia and Hepatitis C Virus Infection: A Rare Association

Smoking-Related Interstitial Lung Diseases

Smoking-related interstitial lung diseases (ILDs) are a group of heterogeneous, diffuse pulmonary parenchymal disease processes associated with tobacco exposure. These disorders include pulmonary Langerhans cell histiocytosis, respiratory bronchiolitis-associated ILD, desquamative interstitial pneumonia, acute eosinophilic pneumonia, and combined pulmonary fibrosis and emphysema. This review summarizes the current evidence of pathogenesis, clinical manifestations, diagnostic approach, prognosis, and treatment modalities for these diseases. We also discuss the interstitial lung abnormalities incidentally detected in radiologic studies and smoking-related fibrosis identified on lung biopsies.

Desquamative interstitial pneumonia: a systematic review of its features and outcomes

Background

Desquamative Interstitial Pneumonia (DIP) is a rare form of idiopathic interstitial pneumonia (IIP). Data on clinical features, aetiology, prognosis and effect of treatment strategies are limited. We aimed to collect all published cases to better characterise DIP.

Methods

A systematic literature search was performed for all original cases of adult patients with histopathologically-confirmed DIP. Individual patient data were extracted and summarised.

Results

We included 68 individual cases and 13 case series reporting on 294 cases. Most common presenting symptoms were dyspnoea and cough. Pulmonary function showed a restrictive pattern (71%) with decreased diffusion capacity. We found a high incidence (81%) of ever smoking in patients with DIP and 22% of patients had other (occupational) exposures. Characteristic features on high-resolution computed tomography (HRCT) scan were bilateral ground-glass opacities with lower lobe predominance (92%). Treatment and duration of treatment widely varied. Initial response to treatment was generally good, but definitely not uniformly so. A significant proportion of patients died (25% of individual cases) or experienced a relapse (18% of individual cases).

Conclusion

DIP remains an uncommon disease, frequently but not always related to smoking or other exposures. Furthermore, DIP behaves as a progressive disease more often than generally thought, possibly associated with different underlying aetiology.

This systematic review is the most comprehensive collection of published cases of DIP to date and yields novel information about aetiology, clinical characteristics, radiology and pathology features, treatment and outcomes.http://bit.ly/394YRPv

Increased Pulmonary GM-CSF Causes Alveolar Macrophage Accumulation. Mechanistic Implications for Desquamative Interstitial Pneumonitis

Desquamative interstitial pneumonia (DIP) is a rare, smoking-related, diffuse parenchymal lung disease characterized by marked accumulation of alveolar macrophages (AMs) and emphysema, without extensive fibrosis or neutrophilic inflammation. Because smoking increases expression of pulmonary GM-CSF (granulocyte/macrophage-colony stimulating factor) and GM-CSF stimulates proliferation and activation of AMs, we hypothesized that chronic exposure of mice to increased pulmonary GM-CSF may recapitulate DIP. Wild-type (WT) mice were subjected to inhaled cigarette smoke exposure for 16 months, and AM numbers and pulmonary GM-CSF mRNA levels were measured. After demonstrating that smoke inhalation increased pulmonary GM-CSF in WT mice, transgenic mice overexpressing pulmonary GM-CSF (SPC-GM-CSF+/+) were used to determine the effects of chronic exposure to increased pulmonary GM-CSF (without smoke inhalation) on accumulation and activation of AMs, pulmonary matrix metalloproteinase (MMP) expression and activity, lung histopathology, development of polycythemia, and survival. In WT mice, smoke exposure markedly increased pulmonary GM-CSF and AM accumulation. In unexposed SPC-GM-CSF+/+ mice, AMs were spontaneously activated as shown by phosphorylation of STAT5 (signal inducer and activator of transcription 5) and accumulated progressively with involvement of 84% (interquartile range, 55-90%) of the lung parenchyma by 10 months of age. Histopathologic features also included scattered multinucleated giant cells, alveolar epithelial cell hyperplasia, and mild alveolar wall thickening. SPC-GM-CSF+/+ mice had increased pulmonary MMP-9 and MMP-12 levels, spontaneously developed emphysema and secondary polycythemia, and had increased mortality compared with WT mice. Results show cigarette smoke increased pulmonary GM-CSF and AM proliferation, and chronically increased pulmonary GM-CSF recapitulated the cardinal features of DIP, including AM accumulation, emphysema, secondary polycythemia, and increased mortality in mice. These observations suggest pulmonary GM-CSF may be involved in the pathogenesis of DIP.

Desquamative interstitial pneumonia with clinical, radiological and histologic correlation

Respiratory bronchiolitis-associated interstitial lung disease (ILD), desquamative interstitial pneumonia (DIP), and pulmonary Langerhans cell histiocytosis are entities of smoking-related ILD. While clinically regarded as 2 separate forms of idiopathic interstitial pneumonia, DIP, and respiratory bronchiolitis-associated ILD are thought to be representing ends of a continuous spectrum of disease that primarily affects tobacco smokers. This case report presents a 53-year-old female patient who has 58 pack-year smoking history who has been experiencing a dry cough and epigastric pains for 2 years. Open-lung biopsy is performed and histopathology indicated smoking-related interstitial fibrosis. The patient did not stop smoking, which after a year leads to significant clinical deterioration with a notable decrease in diffusion for carbon monoxide capacity. Upon smoking cessation and treatment with corticosteroids, a significant clinical improvement is achieved. In smokers complaining of cough and reduced exercise tolerance and in whom evidence of interstitial fibrosis is demonstrated radiologically, DIP should be considered as a differential diagnosis. Smoking is the exclusive etiologic factor of pathogenesis of DIP.

Desquamative interstitial pneumonia: Risk factors, laboratory and bronchoalveolar lavage findings, radiological and histopathological examination, clinical features, treatment and prognosis

Desquamative interstitial pneumonia is a type of smoking-associated major idiopathic interstitial pneumonia, which is characterized by accumulation of alveolar macrophages in alveolar lumens and septa and develops secondary to mainly active or passive exposure to cigarette smoke. Desquamative interstitial pneumonia mostly occurs in male smokers in association with non-specific symptoms responsive to steroid therapy and has a better prognosis than usual interstitial pneumonia. To date, no large-scale clinical studies have been performed on desquamative interstitial pneumonia patients. Factors responsible for the scarcity of data on the clinical course of this condition include the retrospective nature of the available information as well as its rare occurrence. Despite this, a general consensus exists as to the nature of its symptoms, association with smoking, age and gender distribution, findings of respiratory function tests, steroid responsivity and mortality. The objective of the present review article was to report on desquamative interstitial pneumonia and to describe its etiology, risk factors and clinical features, as well as the laboratory, bronchoalveolar lavage, radiological and histopathological findings, and the treatment and prognosis of affected patients.

Current Concepts in Pathogenesis, Diagnosis, and Management of Smoking-Related Interstitial Lung Diseases

Tobacco exposure results in various changes to the airways and lung parenchyma. Although emphysema represents the more common injury pattern, in some individuals, cigarette smoke injures alveolar epithelial cells and other lung cells, resulting in diffuse infiltrates and parenchymal fibrosis. Smoking can trigger interstitial injury patterns mediated via recruitment and inappropriate persistence of myeloid and other immune cells, including eosinophils. As our understanding of the role of cigarette smoke constituents in triggering lung injury continues to evolve, so does our recognition of the spectrum of smoking-related interstitial lung changes. Although respiratory bronchiolitis-interstitial lung disease, desquamative interstitial pneumonia, pulmonary Langerhans cell histiocytosis, and acute eosinophilic pneumonia have a well-established association with tobacco use, its role and impact on idiopathic pulmonary fibrosis, combined pulmonary fibrosis and emphysema, and connective tissue disease-related interstitial lung diseases is still ambiguous. Smoking-related interstitial fibrosis is a relatively newly appreciated entity with distinct histopathologic features but with unclear clinical ramifications. Increased implementation of lung cancer screening programs and utilization of CT scans in thoracic imaging have also resulted in increased identification of "incidental" or "subclinical" interstitial lung changes in smokers, the ensuing impact of which remains to be studied.

The idiopathic interstitial pneumonias: an update and review

Idiopathic interstitial pneumonias (IIPs) are a group of disorders with distinct histologic and radiologic appearances and no identifiable cause. The IIPs comprise 8 currently recognized entities. Each of these entities demonstrates a prototypical imaging and histologic pattern, although in practice the imaging patterns may overlap, and some interstitial pneumonias are not classifiable. To be considered an IIP, the disease must be idiopathic; however, each pattern may be secondary to a recognizable cause, most notably collagen vascular disease, hypersensitivity pneumonitis, or drug reactions. The diagnosis of IIP requires the correlation of clinical, imaging, and pathologic features.

Smoking-related interstitial lung diseases

Cigarette smoke, a toxic collection of thousands of chemicals generated from combustion of tobacco, is recognized as the primary causative agent of certain diffuse interstitial and bronchiolar lung diseases. Most patients afflicted with these disorders are cigarette smokers, and smoking cessation has been shown to be capable of inducing disease remission and should occupy a pivotal role in the management of all smokers with these diffuse lung diseases. The role of pharmacotherapy with corticosteroids or other immunomodulating agents is not well established but may be considered in patients with progressive forms of smoking-related interstitial lung diseases.

Hepatitis C virus and the lung: implications for therapy

Hepatitis C virus (HCV) infection is a chronic blood-borne disease that affects > 4,000,000 individuals in the United States. The majority of individuals with HVC infection acquire a chronic hepatitis that predisposes them to the complications of cirrhosis and hepatoma. Chronic HCV infection is, however, associated with multiple extrahepatic manifestations as well, including recently recognized effects on the lung. These include primary effects on lung function, as well as secondary effects in the settings of progressive liver disease and drug treatment for HCV. In this article, we discuss the emerging clinical data that support a role for HCV infection in lung disease, describe the multiple pulmonary manifestations of this viral infection, and outline the therapies available for specific pulmonary complications of chronic HCV infection.