Pathology of Vaping-Associated Lung Injury (Supplementary Appendix)

Bottom Line: Vaping-associated acute lung injury shows nonspecific injury patterns. Regardless of the fundamental pattern of injury seen, some symptoms are universally present, sometimes with a lesser number. Although the pathogenesis and the chemical agent(s) responsible for this problem remain unknown, the conditions suggest the possibility of direct lung toxicity from an inhaled noxious agent or agents such as those found in e-cigarettes.

Use of e-cigarette devices has exploded in popularity in recent years. E-cigarettes now represent the most common nicotine-containing products used in the United States, especially among adolescents and young adults. There is increasing recognition that vaping is not entirely harmless, and numerous reports of vaping-related pulmonary illness have begun to emerge in the medical literature and also in the lay press, with a spike in reported cases in recent weeks.

Vaping-associated lung injury represents a form of airway-centered chemical pneumonitis induced by one or more inhaled toxic substances in the aerosolized vapor. It is well known that e-cigarette liquids contain not only propylene glycol and glycerin but may also contain numerous contaminants, including polycyclic aromatic hydrocarbons, nitrosamines, endotoxins, diacetyl, and a wide variety of other organic and inorganic chemicals and flavoring compounds that may not be entirely inert.

This study examines 17 patients with clinically suspected vaping-associated acute lung injury. The pathogenesis of vaping-associated acute lung injury remains poorly understood, but much attention has been given recently to the possibility that this may represent a form of exogenous lipoid pneumonia.

All patients had bilateral ground glass and/or consolidative opacities on imaging. The imaging in six of the cases showed a distinct bronchocentric distribution of opacities. No consistent upper versus lower lobe distribution of imaging abnormalities was noted. Although the changes varied, all cases showed one or more patterns or features of acute lung injury. Two patients succumbed to their illness, and five were improving or improved at the time of last follow-up.

Distinguishing vaping-related lung injury from autoimmune disease can be challenging, but a thorough clinical and laboratory workup with testing should enable this distinction in most cases. Distinguishing vaping-related lung injury from pneumonitis induced by other drugs or inhaled toxins may be particularly challenging, especially in patients who may be reluctant to admit use of e-cigarettes or the types of substances vaped. 

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