[Clinical characteristics and genetic features of benign infantile epilepsy with PRRT2 mutation]

Objective: To summarize the detailed clinical characteristics and genetic features of benign infantile epilepsy with PRRT2 mutation, in order to improve the understanding of the disease. Methods: The clinical data and genetic results of 40 benign infantile epilepsy patients with PRRT2 mutation who were diagnosed and treated in the neurology department of National Center for Children's Health (Beijing) , Beijing Children's Hospital affiliated to Capital Medical University from January 2002 to October 2017 and their affected family members were analyzed. Results: Forty benign infantile epilepsy patients were recruited for this study, with 18 males and 22 females. The age at onset ranged from 3 to 15 months (median: 4.6 months). All patients presented focal seizures with or without secondary generalization. Decreased responsiveness, eyes stare and cyanosis were commonly observed. A cluster of seizures was observed in 20 patients at the beginning of the disease, but interictal clinical conditions were normal. Interictal electroencephalograms were normal in 32 cases but 8 cases showed small amount scattered spike and spike wave. Two patients developed paroxysmal kinesigenic dyskinesia in 30 months and 12 years respectively after the cessation of the seizure. Thirty-four affected pedigree members had a history of paroxysmal episodes in 24 families, including 19 individuals of infantile afebrile convulsion, 6 individuals of paroxysmal kinesigenic dyskinesia during childhood or adulthood, 8 individuals of infantile convulsion and paroxysmal kinesigenic dyskinesia during adulthood, one individual of infantile febrile convulsion. The follow-up time ranged from 6 months to 15 years. Thirty-six patients were treated with antiepileptic drugs and their seizures were easy to control. Four patients stayed seizure free without medication (all <2 years). Seizure stopped in 24 patients within 1 year of age, in 10 patients stopped during 12-24 months and in 2 patients stopped during 24-36 months. All cases had PRRT2 mutations, 7 cases of a complete PRRT2 deletion, 33 cases of PRRT2 heterozygous mutations consisted of 28 frameshift mutations and 5 missense mutations. Of these heterozygous mutations, 30 cases were hereditary mutations while 3 were de novo mutations. Nine family members harbored the same PRRT2 mutations without any symptom. Conclusions: Benign infantile epilepsy with PRRT2 mutation is characterized by early onset of seizure mostly before 6 months, focal seizures with or without secondary generalization, a high incidence of a cluster of seizures, rapid resolution of seizure by antiepileptic drugs and cessation of seizure mostly before 2 years of age. Partial patients may develop paroxysmal kinesigenic dyskinesia increasing with age. Most PRRT2 gene mutations are heterozygous mutations, and a few are the overall deletion of PRRT2 gene.