"it is really the case" is correct and usable in written English.
You can use it to emphasize that something is certain or true. For example, "It's been many years since we last saw each other, but it is really the case that I haven't forgotten our friendship."
We may point out that, even if it is really the case, as certain persons assert, that the existent is infinite and motionless, it certainly does not appear to be so if we follow sense-perception: many things that exist appear to be in motion.
Furthermore, it is not clear that it is really the case that pictures cannot be inexplicit in the relevant way (consider, for example, a rough, impressionistic sketch of a tiger, or a blurred photograph).
Author's Response Yes, it is really the case.
If it is really the case that the parasites do not form a clan, it therefore seems likely that the gain-loss model used is still an inadequate description of the real process of genome evolution.
Besides, if it's really the case that the result of a study hinges on a specific nuance of the experimenter's own behavior, then that's an interesting area to research in and of itself.
Even if there are, then, negative consequences in terms of distress to the family, friends, and loved ones, of the person who kills themself, that might still be outweighed by the benefit to the person himself or herself, if it was really the case that he or she would be better off dying.
Here, it's really the case.
There's this famous sentence you can read here and there, "J Dilla changed my life," and it's really the case for me.
If that is really the case, it makes you question all of the outrage being directed at Goldman over this transaction.
At the same time it is not clear, if this is really the case and which alternative approach would be more suitableg.
It remains to be investigated whether this is really the case.
