Mixed-dust pneumoconiosis: Review of diagnostic and classification problems with presentation of a work-related case

Abstract

Environmental aerosolized particulates pose a potential risk to human health worldwide. Among others, high amounts of contaminants are generated especially in newly industrializing countries in the vicinity of industrial manufacturing, mining operations, but also during agricultural and natural processes. As an example of the needed multi-disciplinary diagnostic and differential diagnostic approach, we report a case of a 59-year old industrial worker who has suffered from chronic bronchitis and progressive dyspnea on exertion for 8years. He showed severe lung function impairment, a cavity in his right upper lung lobe, nodular and irregular opacities, fibrotic pleural changes and emphysema. According to the occupational history and the industrial hygiene report, he had been engaged in the production of various refractory materials and been exposed to very high levels of inorganic dust, especially to silica, silicon carbide and aluminum compounds, but also to carbon and other dusty materials for 28years. Histopathology of the two resected lung segments showed focally infarcted granulomas and chronic inflammation. Stains for organisms were negative. The lung tissue away from the granulomas showed significant dust deposition including dust macules. In spite of the inorganic dust deposits, with adjacent tissue lesions evident from the radiological findings (which were interpreted as atypical for pneumoconiosis) and the presence of granulomas in lung tissue, a diagnosis of necrotizing sarcoid granulomatosis was made, which was later changed to mixed-dust pneumoconiosis on further detailed examination. Scanning Electron Microscopy/Energy-Dispersive X-ray Spectroscopy (SEM/EDS) analysis of individual particles showed predominantly Si (silica or silicon carbide [SiC]) and Al particles (consistent with aluminum metal and/or oxide), as well as numerous Al silicates, Ti, and occasional Zr, Nb, V, steel, including Si fibers (consistent with SiC). We present the controversy about the pathogenesis of the lung disorder and whether it represents an occupational disease - which is more or less representative for many such cases.