Recently, whole exome sequencing of patient GBM samples identified a heterozygous missense mutation in the metabolic enzyme isocitrate dehydrogenase (IDH), which was found to be present in 70–80% of WHO grade II–III gliomas, namely astrocytomas and oligodendrogliomas, and secondary GBM (6, 7). Here, IDH3A is linked to glioma.