Ring 20 chromosome syndrome with epilepsy and dysmorphic features: a case report.

Relatively few cases of the 20 ring chromosome [r(20)] syndrome have been reported. Epileptic seizures, behavioral problems, mental retardation, and absence of definite dysmorphic features characterize this syndrome. We present a patient with the classic genetic and phenotypic findings. A 42-month-old boy with mild dysmorphic features and psychomotor retardation has had generalized tonic-clonic seizures, resistant to antiepileptic drug therapy since he was 26 months old. Electroencephalography (EEG) was performed on several occasions, as were brainstem auditory evoked potentials (BAEPs), magnetic resonance imaging (MRI), and cytogenetic studies. The EEG showed slow waves in anterior regions intermingled with spikes in temporal areas. The BAEPs were abnormal, and neuroimaging studies were normal. The chromosome r(20) appeared in 100 metaphases studied. Parental chromosomes were of normal karyotype. The genetic and EEG finding from this patient strongly suggest that epilepsy associated with 20 ring chromosome syndrome is a distinct new entity, although the clinical manifestations may be broader than previously recognized.