Clinical features and gene analysis of TBC1D24 gene mutation related early-onset focal myoclonic epilepsy

Abstract

Objective: To investigate the clinical features and genetic characteristics of patients with TBC1D24 gene mutation related early-onset focal myoclonic epilepsy. Methods: Clinical data of 3 patients with TBC1D24 gene mutation related early-onset focal myoclonic epilepsy of Xuanwu Hospital from November 2016 to June 2017 was collected and analyzed.Candidate gene mutations were screened by second generation sequencing. Results: Among the 3 patients, 1 was male and 2 were females.Seizure onset age was 4 months, 3 years and 5 years after birth respectively. Two patients had family history of epilepsy.They all had prolonged episodes of focal myoclonus. Two patients had mental retardation.Scalp electroencephalograms (EEG) was recorded in all 3 cases and myoclonic seizures were captured.The ictal EEGs were normal in all cases. In one patient, the ictal EEG of generalized seizure showed alpha rhythm originating from left fronto-central region. Brain magnetic resonance imaging (MRI) was normal in 2 patients. Abnormal signal was found bilaterally in cerebellum in 1 patient. The gene screening showed that two patients carried compound heterozygous mutation of TBC1D24 gene and one carried homozygous mutation, all of which were de novo mutations.All the patients were treated with multiple antiepileptic drugs (AEDs) and seizures were uncontrolled in 2 patients. One patient was followed up for 10 months without recurrence. Conclusions: TBC1D24 gene related early-onset focal myoclonic epilepsy is clinically characterized by early onset, prolonged focal myoclonus which relieved with sleep, mental retardation and poor response to AEDs.The interictal and ictal EEG usually show normal. Genetic analysis can assist in diagnosis and genetic counseling.