Hard metal lung disease: high resolution CT and histologic correlation of the initial findings and demonstration of interval improvement.

Hard metal lung disease (HMLD) is a rare form of interstitial lung disease caused by sensitization to cobalt. It occurs in patients exposed to hard metal (tungsten carbide) and in diamond workers who use cobalt-containing polishes. The chest radiograph may be normal or show a nodular, reticulonodular, or reticular pattern. The high-resolution CT findings have been described in a small number of patients. Reported abnormalities include patchy lobular ground glass opacities, consolidation, reticulation, centrilobular nodularity, and, occasionally, honeycombing.We describe the high-resolution CT findings in a patient with pathologically proven HMLD who demonstrated interval improvement in the ground glass opacities and persistence of the centrilobular nodules following cessation of exposure to hard metal and treatment with corticosteroids. To our knowledge, this is the first described case of HMLD with follow-up CT examination.