ATP1A3 and infantile epileptic encephalopathy: Clinical differentiation of AHC should include other disorders of the group of ATP1A3-related disorders.46 The disorders that most commonly overlap in clinical manifestations with AHC are RPD and CAPOS syndrome (Figure 3) (Table 3).47 But other conditions should also be considered due to similarities in clinical presentation, such as early infantile epileptic encephalopathy (EIEE), relapsing encephalopathy with cerebellar ataxia, and childhood rapid-onset ataxia.48,49