Chest Imaging

Siderosis

(also called iron pneumoconiosis), pneumoconiosis caused by long-term exposure to iron (metallic iron and iron oxide). Significant occupational exposure to iron occurs mainly in iron ore mining, in iron and steel foundries, and in welding. Siderosis is often considered as the prime example of a 'benign pneumoconiosis'. This term is used to label those pneumoconioses which generally have a favourable prognosis because they are caused by relatively inert (i.e. nonfibrogenic) dusts, in contrast to those that may evolve towards debilitating pulmonary fibrosis, i.e. mainly silicosis, asbestosis and coal workers pneumoconiosis. In this sense, benign pneumoconioses may be viewed as radiological disorders, rather than as true diseases. However, there are objections, not least from the point of view of prevention, against labelling a dust-induced disease as benign and there are occasional individuals (e.g. welders) in whom these so-called benign pneumoconioses do cause significant impairment. Clinically, the important issue in relation to 'benign pneumoconioses', is to make a correct differential diagnosis in order to avoid potentially dangerous and unnecessary interventions.

Iron dust has a high radiodensity and, consequently, the standard chest radiograph shows a variable, usually large number of small opacities varying from 0.5 to 2 mm in diameter, of striking density. Confluence does not occur. Hilar lymph nodes appear unusually radiopaque but they are not enlarged. The opacities may gradually disappear after cessation of exposure. Other inert dusts of high radiodensity (barium, antimony, tin) may produce similar appearances. In mining, but also in foundries, there is often concomitant exposure to quartz, which may lead to a mixed pneumoconiosis, called siderosilicosis.

JV