Alternating Hemiplegia of Childhood (AHC) is an ultra-rare neurological disorder characterized by transient episodes of hemiplegia, which is weakness or paralysis, that individuals with the condition experience. AHC typically presents before the age of 18 months and can cause anything from mild weakness to complete paralysis on one or both sides of the body. The disorder is highly variable and unpredictable, with symptoms that may affect one side of the body or the other (hemiplegia) or both sides of the body at once (quadriplegia).
In addition to hemiplegic episodes, individuals with AHC may experience intermittent abnormal eye movements, episodes of muscle stiffness or posturing (dystonia), and seizures. The specific symptoms and severity of AHC can vary widely among affected individuals. The disorder is caused by mutations in the ATP1A3 gene in the majority of cases, while a small number of cases are caused by mutations in the ATP1A2 gene.
AHC is a complex and heterogeneous disorder, with hemiplegic episodes being just one of several clinical dysfunctions that can involve the autonomic nervous system, musculoskeletal system, and brain, including seizures and cognitive impairment. Many affected children also display some degree of developmental delay, abnormal eye movements, uncontrolled limb movements (including ataxia, dystonia, and choreoathetosis), and seizures.
The management of AHC requires lifelong care, and treatment options are focused on symptom management and supportive care. A comprehensive approach involving a team of specialists, including neurologists, cardiologists, child behavioral health experts, medical geneticists, and various therapists, is often necessary to provide the best possible care for individuals with AHC.
