Alternating Hemiplegia of Childhood and Developmental Delay: A Longitudinal Pediatric Neurogenetic Case Report

Background Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disorder most commonly caused by pathogenic variants in ATP1A3 . It is characterized by recurrent episodes of alternating hemiplegia, paroxysmal neurological manifestations, developmental delay, and epilepsy. Access to molecular diagnosis remains limited in many low- and middle-income countries, contributing to delayed recognition and management. Case Presentation This case report describes a female patient with paroxysmal alternating hemiplegic episodes, developmental delay, and epilepsy. Hemiplegic events were characterized by alternating laterality and remission during sleep at 2 years and 10 months of age. Neuroimaging was largely unremarkable, including a structurally normal brain CT at 14 years of age, without evidence of vascular or progressive structural pathology. Genetic testing identified a heterozygous pathogenic variant in ATP1A3 (c.2839G>A; p.Gly947Arg), confirming the diagnosis of ATP1A3-related AHC. An additional CDKL5 c.2156C>T variant of uncertain significance was detected but was not clinically contributory based on phenotype correlation. Multidisciplinary follow-up showed partial response of hemiplegic episodes to flunarizine and preserved cardiac structure and function. Conclusion This case reinforces the clinical and genetic heterogeneity of ATP1A3 -related alternating hemiplegia of childhood and highlights the importance of molecular confirmation for accurate diagnosis and management. In resource-limited settings, delayed access to genomic testing may prolong the diagnostic odyssey. Strengthening neurogenetic diagnostic capacity in Latin America is essential to improve early recognition, guide precision-based treatment strategies, and reduce healthcare inequities for patients with rare neurodevelopmental disorders.