special subjects
Metal Fume Fever and Polymer Fume Fever
Diagnosis
Clinical evaluation Chest x-ray ECG There are no definitive diagnostic tests for metal fume fever; diagnosis relies largely on history and physical examination. Metal fume fever is diagnosed when workers or others with a history of exposure to zinc fume (eg, welders) present with the characteristic symptoms of the syndrome. Because the symptoms are similar to influenza symptoms, an occupational or exposure history is necessary to avoid a delay in diagnosis. The most common objective findings are fever and sinus tachycardia. Other findings are typically more subjective and may include rigors and diaphoresis. Pulmonary examination is typically normal with normal respiratory rate, effort, and chest wall excursion; rales or wheezing is occasionally heard. When metal fume fever is severe, pulmonary examination detects respiratory distress, wheezes, rales, and/or rhonchi. Because severe metal fume fever is rare, alternative diagnoses (eg, cadmium pneumonitis, other causes of ARDS) should be considered. Chest x-rays are typically normal in metal fume fever but help differentiate metal fume fever from other causes of similar symptoms, such as pneumonia. Mild vascular congestion may be present but is nonspecific. When metal fume fever is severe, chest x-rays show diffuse bilateral patchy infiltrates, as occur in ARDS. CT of the chest, if done, typically shows bilateral mild atelectasis and pleural effusion. In severe cases, CT may show bilateral diffuse alveolar or ground-glass opacities. Laboratory tests, if done, may detect nonspecific leukocytosis with a left shift. Inflammatory markers (eg, erythrocyte sedimentation rate, C-reactive protein) may be elevated. In case reports, serum zinc levels were elevated during acute episodes, but this testing is not available in the acute care setting and therefore is of little clinical use. Pulmonary test results, usually not needed immediately, may be normal or indicate slightly decreased vital capacity, which resolves when symptoms resolve. In severe cases, a Restrictive disorders may be present. Diagnosis of pulmonary fume fever is also clinical; it is based on a history of occupational exposure to heated PTFE or to overheated Teflon® cookware, followed by the onset of the characteristic symptoms of this syndrome. The characteristic symptoms and signs and diagnostic testing results are the same as those for metal fume fever, except polymer fume fever does not cause tachyphylaxis. 