[Genotype-phenotype correlation in patients with alternating hemiplegia of childhood]

Objective: To explore the correlation between ATP1A3 genotype and phenotype in children with alternating hemiplegia of childhood (AHC). Methods: This was a retrospective study. The clinical data and peripheral blood DNA of AHC patients were collected in Peking University First Hospital from August 2005 to December 2017. ATP1A3 gene mutations were screened by Sanger sequencing or next generation sequencing (NGS). AHC patients were divided into difference groups according to different hotspot mutations. SPSS 23.0 was used to analyze the correlation between genotype and phenotype. Variance analysis was used to compare the measurement data between groups. Chi square test was used to compare the categorical data between groups. Kruskal-Wallis test was used to compare the unidirectional ordered data between groups. Least-significant difference(LSD) was used to compare the data between two groups. Results: A total of 119 AHC patients were recruited, including 68 males and 51 females. The onset age of 113 (95.0%) patients was within 18 months. There were 119 cases (100.0%) with hemiplegic seizures, 109 cases (91.6%) with abnormal eyeball movements, 104 cases (87.4%) with dystonia, 31 cases (26.1%) with autonomic neurological symptoms, 31 cases (26.1%) with epileptic seizures and 117 cases (98.3%) with long-term developmental delay. In 113 patients (95.0%) with ATP1A3 gene mutations, 111 were de novo mutation and 2 were genetic mutations. A total of 39 mutation types were found, including 37 missense mutations and 2 deletion mutations. Seventeen of them were novel mutations. The three hotspot mutations were D801N (n=34, 30.1%), E815K (n=20, 17.7%) and G947R (n=13, 11.5%). The age of onset of D801N and E815K were earlier than G947R ((3.1±2.1)and (2.3±2.3)vs.(6.4±7.7) months, P=0.004 and 0.003). The age of first hemiplegic events of D801N and E815K were earlier than G947R((6.4±3.1) and (6.8±3.3) vs. (11.4±10.1) months, P=0.004 and 0.016). More patients with E815K mutations presented epilepsy than those with D801N (P=0.003) and G947R (P=0.001). More patients with E815K mutations presented greater motor and intellectual disability than the patients with D801N (P=0.001) and G947R mutations (P=0.001). Conclusions: ATP1A3 gene is the main causative gene of AHC. Three hotspot mutations, D801N, E815K and G947R, were found. Hotspot mutation E815K is associated with the most severe phenotype, which presented an earlier age at the time of the first paroxysmal manifestation and first hemiplegic event, severer developmental delay and a greater proportion of epilepsy.