https://isd.hscic.gov.uk/rsp-snomed/user/guest/request/view.jsf?request_id=138 Request 138 (which I noted a couple of years ago on the other forum) was for addition of the Synonym terms: Myalgic Encephalitis Myalgic Encephalopathy under the Synonym list for Concept SCTID 52702003 | Chronic fatigue syndrome (disorder) | This request had been submitted on 18/05/09 and was accepted and implemented. These two terms are exclusive to the UK Edition. The search engine does not return a result for "Medically unexplained symptoms" so I've not been able to determine in which year this SNOMED CT Concept term was requested and implemented. (The database may not go back that far.) This term is exclusive to the UK edition. The UK Edition and all other Editions include a Concept term for "Medically unexplained symptom" - but the UK Edition is the only edition to include a Concept term for "Medically unexplained symptoms".