She had Snijders Blok-Campeau syndrome, which is caused by mutations in the CHD3 protein, which manages the structure of DNA. In her case, it was this missense variant: https://www.ncbi.nlm.nih.gov/clinvar/variation/422607/

The severity of Snijders Blok-Campeau syndrome can vary, but it sounds like Mei only suffered from mild intellectual disability.

https://en.wikipedia.org/wiki/Snijders_Blok%E2%80%93Campeau_... https://www.nature.com/articles/s41586-026-10113-6