A 29-year-old man is seen in the chest clinic. A week ago he was seen in the ER with symptoms of headache, fever, and metallic taste in his mouth. He denied any specific respiratory symptoms. It was noted in the ER record that he had a history of substance abuse. His physical exam was normal except for needle tracks in his right arm. At that time, before a complete evaluation was done, he left the ER against medical advice. A CXR done in the ER is retrieved . The patient is currently asymptomatic and came to the clinic because he wanted a general checkup.Based on the chest x-ray, the most likely diagnosis is

The PA view demonstrates a normal cardiac silhouette. The pulmonary aeries are not enlarged. There is an elongated opaque metallic density with irregular margins in the left medial costophrenic angle. The pulmonary parenchyma is studded with small nodular and linear opaque densities. These findings suggest intravascular embolization. The inhalation, ingestion, or injection of mercury can produce toxicity, and the clinical scenario described is of an individual who has a history of intravenous substance abuse. The symptoms of headache, fever, and metallic taste in the mouth may follow intravenous injection of mercury. In severe cases, dyspnea, chest pain, and respiratory failure may develop. Metallic mercury can be introduced through an IV site. Foreign body granulomas may form in the lung without any systemic toxicity or demonstrable damage of the pulmonary vascular bed. CXR changes with metallic densities and spherules may remain for many years. The spherical shape of the mercury droplets can be differentiated from shrapnel, which has angular margins, and lymphangiographic dye, which presents as a diffuse haze. Barium and bronchographic contrastmaterial produce a more linear opacity. Other forms of granulomas or inhalation exposure do not produce these chest radiograph changes.