RESUMEN
BACKGROUND Infantile spasms is an age-specific epilepsy syndrome that occurs during infancy and is characterized by tonic and/or flexor-extensor spasms, hypsarrhythmia on electroencephalography (EEG), and neurodevelopmental regression. Adrenocorticotropic hormone (ACTH) is considered one of the main therapies for the treatment of infantile spasms, but despite its great efficacy, it is still associated with potential adverse effects. CASE REPORT Four patients previously diagnosed with infantile spasms were treated with ACTH following the usual treatment regimen. All patients developed asymmetric, involuntary movements, with phenomenology characteristic of dyskinesia. The patients did not manifest loss of consciousness, and the EEG did not show epileptic activity during those episodes. In all cases, involuntary movements disappeared after the completion of the hormonal therapy. CONCLUSIONS The adverse effect of hormonal therapy in infantile spasms is not well known in the literature and could be mistaken as seizures, leading to inappropriate management.