The most likely explanation for the massive quantity of carbon pigment found in the above sample is this patient's history of crack cocaine abuse. Many authors have reported similar findings in both BAL and pleural fluid from crack cocaine smokers. Crack is formed by boiling a mixture of cocaine, baking soda and water until it becomes a waxy substance. This substance is smoked in a glass pipe. As the pipe is smoked a tarry residue forms on the bowl of the pipe.
Many addicts collect the tarry residue and re-smoke it along with more crack.
Frequent deep inhalation of these nonvolatilized impurities overloads the normal macrophage clearing mechanism of the lung and results in the accumulation of large amounts of intracellular and extracellular carbon pigment. In vitro study of the function of alveolar macrophages isolated from cocaine smokers has revealed a decrease in the ability of these cells to kill bacteria and tumor cells. The long term effects of carbon pigment accumulation and decreased macrophage function in these patients remains unknown. Many of the reported patients with increased carbon laden macrophages had a similar presentation to the patient discussed here. Most had cough, shortness of breath and chest pain as well as focal or diffuse lung infiltrates.