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Landau-Kleffner syndrome (LKS) is a rare neurological syndrome characterized by the sudden or gradual development of aphasia (the inability to understand or express language) and recurrent seizures (epilepsy). Males are more often affected by LKS than females. In about 20% of people with LKS, genetic changes (changes) in the GRIN2A gene have been identified. The syndrome is inherited in an autosomal dominant manner. In other cases, the syndrome may be caused by changes to other unidentified genes. LKS is diagnosed when a doctor sees clinical features that are consistent with the syndrome such as a loss of speech and an electroencephalogram (EEG) that shows specific kinds of seizure activity. Genetic testing can be used to confirm if there is a genetic change in GRIN2A, but this testing is not done routinely.