Mutations in BRAT1, encoding BRCA1-associated ATM activator 1, a protein implicated in the cellular response to DNA damage and maintenance of mitochondrial homeostasis1–3, were initially associated with lethal neonatal rigidity and multifocal seizure syndrome (RMFSL, OMIM 614498), a neurological disorder characterized by microcephaly, hypertonia, epilepsy, seizures and death within two years of birth4–6. Here, BRAT1 is linked to Hypertonia.