PhpStorm updates are usually patch-based: they are applied to the existing installation and only require you to restart the IDE. Due to the current limitations of the update system, these patches can only be applied sequentially, on top of one another. For example, if you are using PhpStorm 2017.1.1, you can patch it to 2017.1.2, but not to 2017.1.3.
If you skip or ignore a patch, you will lose