An e-cigarette user has been diagnosed with a rare form of lung scarring which is usually seen in metal workers, according to a study.
The study, published in the European Respiratory Journal, is the first known case where the disease called hard-metal pneumoconiosis has been linked to vaping, researchers said.
The condition creates an unusual and distinctive pattern of damage to the lungs that results in breathing difficulties, according to the researchers at the University of California, San Francisco, US.
It is typically diagnosed in people who work with "hard metals", such as cobalt or tungsten, in jobs like tool sharpening, diamond polishing or making dental prosthetics, they said.
"Hard-metal pneumoconiosis is diagnosed by looking at a sample of patient's lung tissue under the microscope," said Professor Kirk Jones from the University of California, San Francisco.
"It has a distinctive and unusual appearance that is not observed in other diseases. When we diagnose it, we are looking for occupational exposure to metal dust or vapour, usually cobalt, as a cause," Jones said in a statement.
"This patient did not have any known exposure to hard metal, so we identified the use of an e-cigarette as a possible cause," he said.
Hard-metal pneumoconiosis causes damaged lung cells to engulf other cells and form 'giant' cells that can be seen clearly under a microscope.
It can result in permanent scarring in patients' lungs with symptoms such as breathing difficulties and chronic coughing.
This scarring cannot be cured, although some patients may have mild improvement if the exposure to hard-metal dust stops and they are treated with steroids, the researchers said.
When they tested the patient's e-cigarette, a personal vaping device used with cannabis, the researchers found cobalt in the vapour it released, as well as other toxic metals -- nickel, aluminium, manganese, lead and chromium.