After reading the Mayo Clinic report directly, I have doubts that using the presence of lipid-laden macrophages as a way to diagnose exogenous lipoid pneumonia from vaping is legit. And so does the Mayo Clinic.
In other words, just because they found lipid-laden macrophages it doesn’t mean they are the result of exogenous lipoid pneumonia. Here’s the key part of the Mayo Clinic report showing more deeply why they don’t think vitamin E acetate is the cause:
https://www.nejm.org/doi/full/10.1056/NEJMc1913069
Much recent attention has been given to the possibility that vaping-associated lung injury may represent exogenous lipoid pneumonia.
However, none of our cases showed histologic evidence of exogenous lipoid pneumonia and no radiologic evidence thereof has been found; this calls into question the diagnostic utility of identifying lipid-laden macrophages or performing oil red O staining on bronchioloalveolar lavage fluid as a marker of vaping-associated lung injury, as has been proposed.
The significance of this observation remains unclear, particularly in patients with a known vaping history; until more data accumulate, our observations suggest that this finding should be interpreted with caution, as it may simply be a marker of exposure and not necessarily a marker of toxicity.
Although it is difficult to discount the potential role of lipid, we believe that the histologic changes instead suggest that vaping-associated lung injury represents a form of airway-centered chemical pneumonitis from one or more inhaled toxic substances rather than exogenous lipoid pneumonia as such, but the agents responsible remain unknown.