...
For some reason, MedDRA has been structured so that every term at the second-lowest level of its hierarchy (PT - Preferred Term) has a synonymous term at it's lowest level (LLT - Lowest Level Term). The LLT member of each of these pairs has been removed from our Cochrane Vocabulary, so there should be no exactly identical terms within MedDRA. If Update: most of these synonymous terms have been removed, but if you uncover any examples in the course of annotation or QA, please flag them up for us to resolve. However, there will be many close matches within MedDRA - for example UK and US spellings of a term (oedema, edema etc.) are separate terms in MedDRA. We are in the process of resolving this in a way that will merge these MedDRA synonyms.
...