West syndrome associated with mosaic Down syndrome

We report a girl with West syndrome associated with mosaic Down syndrome. She had repetitive tonic spasms at 6 months and an electroencephalography (EEG) showed hypsarrhythmia. Her facial appearance was normal and she had no minor anomalies. Her karyotype was mosaic(46,XX/47,XX,+21). Adrenocorticotropin (ACTH) therapy was effective, and her developmental quotient was 76 at 17 months. This report re-emphasize that chromosomal analysis is recommended for epileptic patients with infantile onset when the cause is unclear