Replacement or removal of features from a claim, as well as the addition of further features, may introduce fresh subject-matter not only in the claim itself, but also in the claims when considered as a whole. In fact, such amendments could result in a combination of features not disclosed in the application as filed when the amended claim is considered together with its dependent claims and/or the claims on which it depends.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/h_v_3.htm
Date retrieved: 17 May 2021