Inborn errors of metabolism arising from mutations to the genes for either of the 2-HGDH isoenzymes or CTP, can lead to accumulation of either 2HG enantiomer resulting in 2-hydroxyglutarate aciduria, with a possible increase in tumour progression [21] with associated poor patient outcomes.[22] Mosaic IDH mutations are characteristic of Ollier and Mafucci syndrome, which manifests raised tissue 2HG and osteoid tumours, and of specific IDH mutations, which are associated with increased risk of glioma formation [23]. Here, IDH2 is linked to glioma.