Lodder-Merla Syndrome, Type 2, with Developmental Delay and with or Without Cardiac Arrhythmia, also known as language delay and attention deficit-hyperactivity disorder/cognitive impairment with or without cardiac arrhythmia, is related to gnb5-related neurodevelopmental disorder. An important gene associated with Lodder-Merla Syndrome, Type 2, with Developmental Delay and with or Without Cardiac Arrhythmia is GNB5 (G Protein Subunit Beta 5). Related phenotypes are delayed speech and language development and hyperactivity