Variants in the ATP1A3 Gene Mutations within Severe Apnea Starting in Early Infancy: An Observational Study of Two Cases with a Possible Relation to Epileptic Activity

Mutations in the ATP1A3 gene are known to cause alternating hemiplegia of childhood (AHC) and rapid-onset dystonia parkinsonism (RDP). Both conditions are childhood-onset neurological disorders with distinct symptoms and different times of onset. ATP1A3 has also been associated with CAPOS syndrome (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss). Within the various ATP1A3-related neurological syndromes, a specific genotype-phenotype correlation is starting to emerge. Several mutations such as the relatively common p.E815K pathogenic variant have been shown to strongly correlate with AHC, while othersmay cause both AHC and RDP. A significant subset of patients with AHC and RDP are reported to have epileptic seizures. Even though detailed clinical descriptions of seizures in childhood are rare, seizures involving apneic events seem to be frequent in ATP1A3-related neurological disorders. Here, we describe two children with unexplained severe apnea beginning around the first year of life and pathogenic variants in ATP1A3. We hypothesize that the symptoms are early-onset autonomic seizures related to the underlying pathogenic ATP1A3 variants.