IMO, DD1 shows no signs of OCD and certainly not contamination OCD. We certainly have experience of DD2 with that. DD1 is quite the opposite - very slap dash about hygiene. DD2 has refused to see her for a year! The only good thing is DD1 thinks she’s mad, and doesn’t want to see her anyway.
As for RCT, DD1’s genetic metabolic disorder is so rare, there’s the case study of the first family diagnosed with it; then three other case studies of children with it and epilepsy worldwide. One died aged two in status in England, before she could have genetic testing; there’s a Chinese girl and a Korean boy. That’s it. Researchers can write about what testing of the urine shows, and the symptoms people have exhibited; but other than that, nobody knows anything much.
There’s no specialist on it in the UK; and only one other family we know of, and they don’t have epilepsy. Two neurological hospitals disagree as to whether it causes epilepsy or not; and what treatment there is, if any?
It’s not at all helpful to know what is wrong with DC, when nobody knows anything much about it, and they disagree about what they think.