Supplementary Material for: Unraveling Alternating Hemiplegia of Childhood: A Case Report with Genetic and Clinical Insights

Introduction: Alternating Hemiplegia of Childhood (AHC) is a complex neurological disorder comprising paroxysmal episodes of repeated, transient paresis involving either or both sides of the body, with onset usually before the age of 18 months. The etiology is varied and includes channelopathy, mutations of ATP1A3 gene that encode alpha subunit of NA+-K+ ATPase pump.
Case presentation: A 7-month-old girl presented with tonic neck deviation of the neck and eyes, episodic hemiparesis affecting both sides alternatively. Each episode resolved after sleep and was precipitated by hunger, fever, and sleep deprivation. Neurological examination and lab workup, including MRI and EEG, were normal. Whole-exome sequencing revealed a heterozygous de novo pathogenic mutation in the ATP1A3 gene (p.Asp801Asn), confirming Alternating Hemiplegia of Childhood. She was started on flunarizine, a calcium-channel blocker. Significant clinical improvement and catch-up in developmental milestones were observed on follow-up.
Conclusion: AHC is frequently misdiagnosed due to its rarity and varied presentation. Diagnosis is clinical and supported by genetic testing. Mutations in ATP1A3 are common and often cluster at specific hotspots. Management includes symptomatic treatment and supportive care, with flunarizine offering some benefit. This case highlights the need for early recognition and genetic confirmation of AHC to initiate therapy and improve quality of life.

引言：儿童交替性偏瘫（Alternating Hemiplegia of Childhood, AHC）是一类复杂的神经系统疾病，以阵发性反复发作的一过性单侧或双侧肢体轻瘫为主要临床特征，通常于18月龄前起病。其病因学多样，涵盖离子通道病以及编码钠-钾ATP酶泵α亚基的ATP1A3基因发生致病性突变。病例报告：1例7月龄女婴，表现为颈项及眼部强直性偏斜，发作性轻偏瘫呈双侧交替累及。每次发作于睡眠后自行缓解，可由饥饿、发热及睡眠剥夺诱发。神经系统查体及实验室检查（含磁共振成像Magnetic Resonance Imaging, MRI与脑电图Electroencephalogram, EEG）结果均未见异常。全外显子测序显示ATP1A3基因存在杂合新发致病性突变（p.Asp801Asn），据此确诊儿童交替性偏瘫。予钙通道阻滞剂（calcium-channel blocker）氟桂利嗪治疗。随访期间可见患者临床症状显著改善，发育里程碑实现追赶式发育。结论：儿童交替性偏瘫因发病率极低、临床表现多样常被误诊。其诊断以临床特征为核心，辅以基因检测佐证。ATP1A3基因突变较为常见，且常聚集于特定突变热点区域。治疗方案包括对症治疗与支持照护，氟桂利嗪可带来一定临床获益。本案例凸显了早期识别儿童交替性偏瘫并通过基因检测确诊，以尽早启动治疗、改善患者生活质量的必要性。