While the 17 biopsies found macrophages - white blood cells that are dispatched to eat harmful contaminants - they found no presence of large deposits of oil or lipids (a kind of fatty organic compound) in the lungs.
She added that little is understood about the relatively new vaping-related lung injuries.
Vaping-associated lung injury can be hard to diagnose, unless clinicians and pathologists are armed with information beforehand, Dr. Larsen says.
A study released by the Mayo Clinic on Wednesday showed that lung illnesses from vaping are most likely a "direct chemical injury", similar to the dangers of being exposed to toxic chemical fumes and poisonous gases.
The findings were published online October 2 in TheNew England Journal of Medicine.
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All of the patients examined had severe forms of the illness, and two had died. Almost three-quarters of those had vaped marijuana or cannabis oil. Two of these patients died.
In the study published yesterday, Mayo's Dr Brandon Larsen and colleagues found no evidence of lipoid pneumonia in any samples they studied. "We have seen a handful of cases, scattered individual cases, over the past two years where we've observed the same thing, and now we are seeing a sudden spike in cases". He's a surgical pathologist at the Mayo Clinic Arizona in Scottsdale.
He said that unless clinicians and pathologists have the information in advance, diagnosing vaping-associated injury can be hard.
"Everyone should recognize that vaping is not without potential risks, including life-threatening risks, and I think our research supports that", he said.
In the meantime, the public should heed what leading medical organizations and public health agencies are saying about the dangers of vaping.
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A recent statement from the CDC offers a reminder that there still seems to be no singular cause or corresponding factor linking all the identified cases outside of straightforward e-cigarette use.
In April, Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine, said the United Kingdom was "out of step" with other parts of the world when it came to messages around the safety of vaping.
While Canada is on high alert for any cases of vaping-related illnesses mulling temporary bans similar to some states south of the border, vape sales seem to be making a comeback in key USA markets. As investigations continue, a number of states have enacted bans on vaping products, and CDC officials have urged Americans not to use e-cigarettes at least until it determines what is causing the growing number of illnesses.
"That these samples do not show evidence of lipid accumulation indicates that the cause is not lipid per se, but something else in the vapour".
So far, 87 per cent of 86 people in IL and Wisconsin who got sick from vaping admitted to having used e-cigarette products containing THC, but 71 per cent also reported using nicotine-containing products.
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All patients in the recent outbreak now under investigation had used an electronic cigarette or other vaping device. Many of the patients reported using numerous vaping products and substances, including a mix of nicotine and THC.
"So it is something in U.S. vape fluids, or something about the particular e-cigarettes used by those affected, but remains something separate from vaping more generally and particularly from vaping nicotine".