Sequencing of the circulating tumor DNAs revealed the presence of mutations in IDH1, IDH2, TP53, TERT, ATRX (nuclear alpha-thalassemia/mental retardation X-linked syndrome), H3F3A, and HIST1H3B mutations claiming them to be significant biomarkers of GBM. Here, IDH2 is linked to X-linked syndromic intellectual disability.