2016). TELO2 forms part of the co‐chaperone triple T complex (TTT complex), along with Tel two‐interacting protein 1 (TTI1; OMIM614425) and Tel two‐interacting protein 2 (TTI2; OMIM614426). Together, this complex plays an important role in the maturation and stabilization of the phosphatidylinositol 3‐kinase‐related protein kinases (PIKKs). Patients with mutations in TELO2 present with intellectual disability, delayed development, microcephaly, postnatal growth retardation and dysmorphic features, which – at least in part – are common features of several PIKK‐related disorders. This evidence concerns the gene TELO2 and microcephaly.