Résumé
Objective To investigate the clinical features,karyotype,and the prenatal diagnosis for his sibling of a Chinese patient with rare ring chromosome 20 syndrome induced intractable epilepsy.Methods The clinical data of the patient diagnosed in Peking University People's Hospital were collected.The clinical manifestations,chromosome karyotype were summarized.Results The proband,a boy,started to show intermittent tonic seizures or atypical absence seizures and psychomotor retardation from the age of 11 months.Several anti-epilepsy drugs and globulin had been tried without effect.Common karyotype analysis and epilepsy-related genes analysis revealed no abnormality.However,abnormal karyotype 46,XY,r(20)(p13q13.3) in his peripheral blood lymphocytes was found by high resolution chromosome karyotype analysis with 550 G-banding,and the diagnosis of ring chromosome 20 syndrome,type Ⅱ was confirmed.The mother of the patient underwent amniocentesis at the midterm of the second pregnancy.The cultured amniocytes karyotypes were normal.The second child(a boy) of the family was 1 year old without epilepsy and the psychomotor development was normal.Conclusions Ring chromosome 20 syndrome is a rare human chromosome abnormality.The syndrome is associated with epileptic seizures,behavior disorders and mental retardation.Since karyotype testing is not a routine investigation for the patient with epilepsy,the diagnosis of ring chromosome 20 syndrome is usually delayed or misdiagnosed.The karyotype analysis should be considered for the etiological study of the patients with intractable epilepsy with unknown origin.