Following excerpts from the above-linked Supplementary Appendix reveal the level of humbling diagnostic complexities and uncertainties that surround attempts to report what are genuinely meaningful observations:
Our aim was to characterize not only the spectrum of clinical and imaging findings in our patients, but also the types of pathologic changes that occur in the lung, to better understand the pathogenesis of this problem and facilitate recognition of the diagnosis in future patients. … All cases of clinically suspected vaping-associated acute lung injury encountered in our clinical and pathology consultation practices with available lung biopsy material were included from three of our institutional sites … Tobacco smoking history, vaping history, and history of illicit drug use was also reviewed, including the duration of these exposures and types of substances used whenever available. … A total of 17 patients met inclusion criteria, including cases from Arizona (n=11), Minnesota (n=5), and Florida (n=1). … Most patients were young adults (median age 35 years, range 19-67) and most were men (76%). Many patients were previously healthy prior to their presentation and had no significant past medical history. … Eight patients had a history of tobacco smoking, but only two were actively smoking at the time of presentation. Four patients had a history of marijuana smoking. … Eleven patients met CDC criteria for a “confirmed” diagnosis of vaping-related lung injury, with the remaining six patients meeting CDC criteria for a “probable” designation, largely due to incomplete information on the autoimmune and infectious disease workup. … All patients had a history of vaping in the weeks and days prior to presentation. Two patients were vaping in an attempt to quit smoking tobacco. Twelve patients (71%) reported vaping tetrahydrocannabinol (THC), cannabis oils, cannabidiol (CBD), or other non-nicotine products. Both manufactured prepackaged vape pods and open access tank style vaporizers were used by subjects. …
… most of our cases showing airway-centered patterns of acute or subacute lung injury with bronchiolitis, foamy macrophage accumulation, and type 2 pneumocyte hyperplasia with vacuolization. Several of our cases showed more severe injury with a pattern of diffuse alveolar damage, including two patients with fatal outcomes. Eosinophils were occasionally seen, but when present, they were never prominent and did not meet histologic criteria for acute eosinophilic pneumonia. It has also been suggested in one case report that vaping may cause hypersensitivity pneumonitis, but this interpretation was based purely on clinical and imaging findings and analysis of bronchioloalveolar lavage fluid, without histologic confirm. Definitive granulomas were not encountered in any of our cases, and none of our cases showed histologic features of hypersensitivity pneumonitis or giant cell interstitial pneumonia from metal fumes.
… 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. … Notably, none of our cases showed histologic features of exogenous lipoid pneumonia … Although none of the individual histologic findings in our cases were specific, foamy macrophage accumulation and pneumocyte vacuolization were universal findings and could be useful diagnostic clues in an appropriate clinical context. This pattern closely resembles the type of changes that are characteristic of toxic reactions to medications (especially amiodarone) or noxious chemical fumes, suggesting a similar mechanism of injury. While it is difficult to discount the potential role of aerosolized lipid accumulation in this injury, no cases showed coalescence of lipid into large droplets as occurs in exogenous lipoid pneumonia. … Our observation is also concordant with the recently reported absence of typical radiologic findings of fat accumulation in the lung that would be expected in exogenous lipoid pneumonia. … To us, the histologic findings would instead seem to suggest that vaping-associated lung injury represents a form of airway-centered chemical pneumonitis induced by one or more inhaled toxic substances in the aerosolized vapor, rather than an exogenous lipoid pneumonia per se. …
… Differential Diagnoses. Adverse reactions to drugs and toxic agents are challenging to diagnose to a reasonable degree of clinical certainty, and this has certainly been true with recent reports of suspected vaping-related lung injury. … In reality, proving causality with absolute certainty can be difficult, even after all alternative etiologies have been excluded. … As with other adverse reactions to drugs and toxic agents in the lung, the histopathologic manifestations of vaping-related acute lung injury are nonspecific, and this is a diagnosis of exclusion. Whether diffuse alveolar damage, acute fibrinous pneumonitis, organizing pneumonia, or other patterns of injury are seen, the differential diagnosis for vaping-related acute lung injury is similar and primarily includes acute infection, autoimmune disease, reactions to other drugs, and other inhalational injuries. … Distinguishing vaping-related lung injury from autoimmune disease can be challenging, but a thorough clinical and laboratory workup with serologic 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. Many medications and illicit drugs have been associated with foamy macrophage accumulation and pneumocyte vacuolization, and to date, no specific histologic features have been noted with any one agent. Furthermore, these features are not specific to drug reactions, and can be seen with acute lung injury from other causes. Based on our observations in our cases, this histopathologic nonspecificity is also characteristic of acute lung injury from vaping, and it would seem that the diagnosis of vaping-related pulmonary illness cannot be made on histologic grounds alone, and is only possible with careful clinicopathologic correlation.
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Reading about the complexities and uncertainties involved in the course of pulmonary medicine diagnoses makes it somewhat easier to understand why a fair number of pulmonologists and epidemiologists have, when interviewed by the “press”, made statements (on the order of, and paraphrased), "if you had told me a year ago that such a medical condition/diagnosis specific to vaping would be found to exist, I would have said “no way’”. (IMO), the CDC and other socio-political players involved (with various monetary or publicity incentives in mind) - having specific pre-baked public policy agendas in mind, and looking for a convenient “shock doctrine” justification (true or not) - are trying to pressure and squeeze the idea of the existence of “problems” fitting their pre-baked “solutions” out of researching physicians, and “selling such” to the so-called “press” - who seem to have little or no qualms about pimping-out utterly false and misleading pseudo-scientific propaganda about physiology that serves as a useful and demonstrably effective subterfuge for what in reality are dominantly Moral Crusades centering around the entirely non-scientific moral pejorative term “addiction”, while revealing the utter dependence of the States upon keeping so-called “Big Tobacco” financially solvent enough for those companies to continue to be able to pay Tobacco Settlement payments. With ~10 Million Nic vapers in US, every day a few will fall ill due to various causes. This seems obvious.
These parasitic festooned ass-clown charlatans are almost entirely uninterested in the illicit THC markets (or the health of such consumers) - because they cannot regulate (and thus, monetarily profit from) them. Their priorities also demonstrate that these players have little interest in public health harm reduction. 
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Dr Michael Siegel’s thoughts (pub Oct 3, 2019) regarding the Mayo Clinic Study published in the NEJM:
