The differential diagnosis of hard metal lung disease.

Hard metal lung disease is usually easy to diagnose, on the basis of occupational history, chest X-ray appearance of interstitial lung disease and, if necessary, by bronchoalveolar lavage (BAL). However, other interstitial lung diseases may affect patients with an occupational history of exposure to cobalt. In hard metal disease, the hylar lymphnodes may enlarge due to high draining of hard metals from the lung tissue via lymphatic vessels. Also, the presence of Giant Cells (even if Langhan's type) in the BAL fluid of sarcoid patients may be high. We present four patients with a history of exposure to hard metals and whose chest X-rays suggest sarcoidosis, stage II; in each, a pulmonary biopsy was necessary to confirm the diagnosis. Final diagnosis was sarcoidosis in one (showing typical granulomata in the lung tissue), and hard metal disease in three: two of these had foreign body-type granulomata in the lung tissue. Neutron activation analysis (NAA) study was carried out on these four patients using specimens of BAL fluid, blood, urine, toenails, pubic hair and sperm. In the light of available data, the concentration of elements may not be useful in differentiating between sarcoidosis and hard metal pneumoconiosis. However, NAA on BAL fluid or other specimens may be helpful in confirming the presence of the offending agent in suspected cases when the occupational history is not clear.