Occupational lung disease (OLD) is a group of lung diseases caused and/or aggravated by organic and inorganic inhaled dust, fumes, and mist. OLD can develop under various occupational situations. Therefore, occupational history should be considered when evaluating respiratory symptoms. Once OLD is developed, it may not be treated and may even progress after exposure to the causative agents has stopped. The best ways to treat OLD are prevention and early detection by controlling the working environment and conducting regular surveillance of workers. Common OLDs in Korea are coal worker's pneumoconiosis, asbestos-related diseases, and occupational asthma. Recent aspects of these common OLDs in Korea will be described based on recently published studies.

Background: Pneumocystis jirovecii is a fungus that has become an important cause of opportunistic infections. We present a summary of the clinical status and findings from bronchoalveolar lavage (BAL) of patients with Pneumocystis jirovecii pneumonia (PJP). Methods: We selected 30 cases of PJP that were proven through a surgical specimen evaluation. BAL fluid cytology was reviewed, and agreement with the initial diagnosis was evaluated. Results: All 30 cases of PJP occurred in immunocompromised patients. Only 15 of the 30 cases were initially diagnosed as PJP. We found PJP in 13 of the 15 cases that were negative at the initial diagnosis. The most characteristic finding of PJP was frothy exudates, and BAL fluid tended to show rare neutrophils. Two of seven patients with PJP and diffuse alveolar damage (DAD) revealed no frothy exudates in BAL fluid. Conclusion: BAL fluid cytology was reconfirmed as a sensitive and rapid method to diagnose PJP. We must be aware of the possibility of PJP to maintain high diagnostic sensitivity. We cannot exclude PJP in cases of PJP with DAD, even if frothy exudates are not observed in the BAL fluid.

Background: Chronic obstructive pulmonary disease (COPD) is a major cause of chronic morbidity and mortality throughout the world and is the only major disease that is continuing to increase in both prevalence and mortality. The second Korean National Health and Nutrition Survey revealed that the prevalence of COPD in Korean subjects aged ${\geq}45$ years was 17.2% in 2001. Further surveys on the prevalence of COPD were not available until 2007. Here, we report the prevalence of spirometrically detected COPD in Korea, using data from the fourth Korean National Health and Nutrition Survey (KNHANES IV) which was conducted in 2007~2009. Methods: Based on the Korean Statistical Office census that used nationwide stratified random sampling, 10,523 subjects aged ${\geq}40$ years underwent spirometry. Place of residence, levels of education, income, and smoking status, as well as other results from a COPD survey questionnaire were also assessed. Results: The prevalence of COPD (defined as forced expiratory volume in 1 sec/forced vital capacity <0.7 in subjects aged ${\geq}40$ years) was 12.9% (men, 18.7%; women, 7.5%). In total, 96.5% of patients with COPD had mild-to-moderate disease; only 2.5% had been diagnosed by physicians, and only 1.7% had been treated. The independent risk factors for COPD were smoking, advanced age, and male gender. Conclusion: The prevalence of COPD was 12.9% in the KNHANES IV data. Most patients with COPD were undiagnosed and untreated. Based on these results, a strategy for early COPD intervention is warranted in high risk subjects.

Background: Community-acquired pneumonia (CAP) is an important cause of morbidity and mortality throughout the world in all age groups. Viral causes of CAP are less well characterized than bacterial causes. We analyzed the characteristics of hospitalized patients with CAP who had a viral pathogen detected by multiplex polymerase chain reaction (PCR). Methods: Multiplex real-time PCR was performed for respiratory viruses in samples collected from 520 adults who developed CAP at Chungnam National University Hospital. Clinical, laboratory, and radiological features at presentation as well as other epidemiological data were analyzed. Results: Of 520 patients with CAP, a viral pathogen was detected in 60 (11.5%), and influenza A was the most common. The virus detection rate in patients with CAP was highest in November. Two or more pathogens were detected in 13 (21.7%) patients. Seven patients had severe disease and were administered in the intensive care unit. Most patients (49/60, 81.7%) had comorbidities. However, nine (15%) patients had no comorbidities, and their age was <60 years. The ground glass opacity pattern was the most common radiological feature. Seven (11.7%) patients died from CAP. Conclusion: Viral pathogens are commonly detected in patients with CAP, and a respiratory virus may be associated with the severity and outcome of pneumonia. Careful attention should be paid to the viral etiology in adult patients with CAP.

Background: The aim of this study was to investigate annual changes in pulmonary function in workers who were exposed to inorganic dust. Methods: The subjects were 2,922 male patients who had been diagnosed with pneumoconiosis more than twice during 6 years from 2005 to 2010. Results: Of the 2,922 cases, forced vital capacity (FVC) decreased by 54 mL in 1 year. In contrast, the annual change of forced expiratory volume in one second ($FEV_1$) decreased by 56 mL. Conclusion: This is the first study that has investigated the annual change in pulmonary function in workers exposed to inorganic dust. The results will help estimate the pulmonary condition of patients who are unable to perform a pulmonary function test due to age or a disorder.

Background: Lung cancer is the leading cause of cancer deaths in the world. Human papillomavirus (HPV) infection and E6 oncoprotein expression are known risk factors for the development of non-small cell lung cancer (NSCLC). This study was performed to evaluate the prevalence of HPV 16/18 E6 oncoprotein expression in patients with NSCLC. Methods: Immunohistochemical stains of the HPV 16/18 E6 oncoprotein were performed in tumor tissues from 68 patients with NSCLC who underwent curative surgery from March 2006 to November 2008. Results: The E6 oncoprotein was expressed in 29.4% of patients with NSCLC and a statistical analysis revealed that E6 oncoprotein expression was significantly higher in females (p=0.028), never smokers (p=0.045), and patients with adenocarcinoma (p=0.022) than that in other patients. Conclusion: The E6 oncoprotein was expressed in 29.4% of patients with NSCLC. Further studies detecting HPV infection and E6 oncoprotein expression in never smoking patients with NSCLC are needed.

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a useful, safe diagnostic modality for evaluating mediastinal and hilar lymphadenopathy. We report a 51-year-old male who presented with a left renal mass and multiple pleural masses without lung parenchymal lesions. The pleural masses were thought to be metastatic tumors or malignant mesothelioma. The patient underwent two percutaneous needle biopsies of the pleural mass, but the specimens were insufficient for a histopathological diagnosis. Because one pleural mass was adjacent to the right main bronchus, we decided to perform EBUS-TBNA for the pleural mass. As a result, sufficient core tissue was obtained with no complications, and the histopathological findings were consistent with metastatic papillary renal cell carcinoma. To our knowledge, this is the first case of using EBUS-TBNA for a pleural mass.

Streptococcus parasanguinis is a Viridans group bacteria that is most often discovered in the oral cavity and causes dental plaque and endocarditis in a rat model. It has low virulence but an unknown relationship to human respiratory infections. We report on a 61-year-old woman who developed hemoptysis followed by pleuritic chest pain after conscious sedation during a gastroscopic polypectomy and was diagnosed with pneumonia and parapneumonic effusion from Streptococcus parasanguinis isolated in pleural fluid. Microaspiration during the procedure was presumed to play a role in the pathogenesis.

Lymphoepithelioma-like carcinoma (LELC) of the lung is a very rare tumor. Originally described in the nasopharynx as lymphoepithelioma, this carcinoma has also been found in the stomach, esophagus, thymus, cervix, urinary bladder, skin, and salivary glands. Histologically, it is an undifferentiated carcinoma that has a syncytial appearance with tumor cells and is infiltrated by numerous lymphocytes, macrophages, and plasma cells. LELC of the lung occurs more commonly in Asians, particularly Chinese. Many studies have reported the association between Epstein-Barr virus (EBV) and LELC of the lung in Asian patients. A 45-year-old man had a solitary pulmonary nodule on a routine chest X-ray examination. As a malignant tumor was suspected, surgical resection was performed to establish the correct diagnosis. The pathology of the excised tumor demonstrated LELC of the lung. This is the first report of LELC of the lung in Korea.

Acute fibrinous and organizing pneumonia is a newly recognized pattern of acute lung injury. A 49-year-old female presented with a cough and worsening dyspnea on exertion. She had no history of smoking and no specific past medical history except exposure of home humidifier containing sterilizer. A chest computed tomography scan showed patchy consolidation with fibrosis in the right lower lobe and ill-defined centrilobular ground glass opacity in both lungs. The pathological findings were patchy areas of lung parenchyma with fibrin deposits in the alveolar ducts and alveoli, and fibrin balls with hemosiderin deposition in the alveolar spaces. The histological pattern of our case is differentiated from diffuse alveolar damage by the absence of hyaline membranes, and from eosinophilic pneumonia by the lack of eosinophils. In our case, the patient was treated with corticosteroid pulse therapy. However, the clinical course became aggravated and she died within two weeks.