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It has been said that adult chest physicians know three diseases—asthma, COPD and lung cancer—and cannot cure any of them. This is of course a libel both in terms of disease numbers and prognosis; however, the response to this libel seems to be to try to create new diseases that do not exist, rather than focus on new areas coming into adulthood, such as survivors of preterm and even late preterm birth.1–3 So ACOS, which might be thought to be some sort of demented lettuce, refers to asthma COPD overlap syndrome (or another, rather ruder acronym which we are tempted to use but with which we probably should not sully the pages of Thorax). This acronym has the demerits of combining what we argue to be two useless umbrella terms to make a third one that is even more useless.
In this issue of the Thorax, Peter Gibson and Vanessa McDonald4 review the published literature on ACOS published since our last review in 2009.5 In total, 20% of patients could not find shelter under either the asthma or COPD umbrella, so a new one has to be sought. Their review makes depressing reading; quite unsurprisingly they found ‘subgroups’ within ACOS—the looming nightmare of ACOS type 1, ACOS type 2 to ACOS type infinity beckons. ACOS may be characterised by a COPD-like systemic inflammatory profile; ACOS, asthma and COPD may be neutrophilic, eosinophilic or mixed; and bronchodilator reversibility fails to distinguish anything from anything else. The authors recommend jettisoning ACOS, with which view we concur; we …