<prompt> All of the following statements about silicosis are true exceptPleural plaquesPrediliction for upper lobesCalcific hilar lymphadenopathyAssociated with tuberculosis  <response>: 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 