Introduction: Alternating hemiplegia of childhood (AHC), is a rare disease characterized by episodes of hemi/quadriplegia, dystonic postures, abnormal eye movements, and movement disorders. ATP1A3 gene mu tations are the most frequently associated with AHC.
Objective: To present a clinical case of AHC, where genetic study and the observation of home videos were of great diagnostic utility.
Clinical case: Female patient who at 3 months of age presented with several episodes of dystonic postures, clonic movements of extremities, cephalic version, and lateral gaze deviation lasting several minutes. Epilepsy was diagnosed and levetiracetam was administrated, without improvement. EEG and brain MRI were performed, with normal results. Therefore, epilepsy was ruled out and transient dystonia of infancy was suspected, however, the events became more frequent, longer in duration, and charac teristically subsided during sleep. Family members provided home videos that clarified the events. At 6 months of age, the patient presented with alternating hemiparesis. Dystonia genetic panel showed a pathogenic variant of the ATP1A3 gene, confirming the diagnosis. Flunarizine treatment was ini tiated with a good clinical response at 12 months of follow-up.
Conclusions: The diagnosis of AHC is complex and is frequently confused with epilepsy, so it is important to correctly perform the diffe rential diagnosis, including anamnesis, tests such as EEG, and careful observation of clinical events that, with the current access to audiovisual technology, becomes more accurate. The genetic analysis is a great diagnostic tool that, when performed in time, avoids other unnecessary tests and therapies.