Inactivating TCF4 mutations has been identified as the cause of the neurodevelopmental disorder Pitt–Hopkins syndrome (PHS; #610954; OMIM) whose symptoms include intellectual disability, failure to acquire language, deficits in motor learning, distinctive facial features, hyperventilation, gastrointestinal abnormalities, and autistic behavior (Zweier et al, 2007; Marangi & Zollino, 2015). Here, TCF4 is linked to Intellectual disability.