All of the following statements about silicosis are true except
With long-term, less intense exposure, small rounded opacities in the upper lobes may appear on the chest radiograph after 15-20 years of exposure, usually without associated impairment of lung function (simple silicosis). Calcification of hilar nodes may occur in as many as 20% of cases and produces a characteristic "eggshell" pattern. Because silica is cytotoxic to alveolar macrophages, patients with silicosis are at greater risk of acquiring lung infections that involve these cells as a primary defense (Mycobacterium tuberculosis, atypical mycobacteria and fungi). Because of the increased risk of active tuber-culosis, the recommended treatment of latent tuberculosis in these patients is longer. Ref Harrison 19th edition pg 1690
Pleural plaques
Prediliction for upper lobes
Calcific hilar lymphadenopathy
Associated with tuberculosis
Respiratory system