>>>THIS<<< is a link to the CHC support thread.
CHC can be granted for any illness or disease, it is granted when a 'primary health need' has been established using the DST.
You could ask SS for more details. The comment about one A being cancelled because he had dementia does not make sense, having dementia cannot cancel any score. One explanation could be that some symptom or event was entered into two domains that were both graded A and then one downgraded because the information had been entered in the other, this is incorrect
In certain cases interdependence between domains can actually be used to upgrade scores using complexity as an argument.