Type Unknown
These are the folk who do not fit into any of the other listed categories. If they like they can think of themselves as the exceptions that prove the rule.
When one thinks of diabetes as a symptom rather than a disease i.e. in type 1 it is a symptom of pancreatic failure, in type 2 of insulin resistance etc, etc then one comes to realise that there are probably a host of ,as yet, unrecognised diseases out there that have diabetes as one of their symptoms.
However, the general rules do mostly apply to them as well.