Two siblings with acute necrotizing encephalopathy associated with variants of LARS1.

Acute necrotizing encephalopathy (ANE) is a rapidly progressive encephalopathy of unknown etiology. The underlying mechanisms are highly heterogeneous, often including genetic backgrounds. Variants of LARS1, encoding the leucyl-tRNA synthetase 1, are responsible for infantile liver failure syndrome 1. We describe two siblings with ANE caused by compound heterozygous variants of LARS1. Patient 1 was a 17-month-old girl. She presented with generalized seizure and liver dysfunction due to influenza type A infection. Brain magnetic resonance imaging on day 4 of onset showed diffuse high-intensity signals consistent with ANE. She died on day 10. Patient 2, a younger male sibling of patient 1, had mild to moderate developmental delay and growth failure at the age of 18 months. He showed a markedly elevated level of transaminases triggered by infection with human herpesvirus 6. On day 4 of onset, he had generalized seizures. Brain computed tomography showed a diffuse symmetrical hypodensity consistent with ANE. He died on day 7. Whole exome sequencing identified the compound heterozygous variants in LARS1 (NM_020117.11) as c.83_88delinsAATGGGATA, p.(Arg28_Phe30delinsLysTryAspIle) and c.1283C>T, p.(Pro428Leu) in both siblings. The severe neurologic phenotype, found in our patients, reflects the complicated pathogenesis of LARS1-related disorder.

Two-year efficacy of lacosamide as adjunctive therapy for generalized tonic-clonic seizures in patients with juvenile myoclonic epilepsy.

OBJECTIVE: To report the long-term efficacy of adjunctive lacosamide therapy in patients with juvenile myoclonic epilepsy whose generalized tonic-clonic seizures were significantly reduced by treatment. METHODS: A retrospective study was conducted in patients who visited the Department of Child Neurology, National Hospital Organization Nishiniigata Chuo Hospital and the Department of Pediatrics, National Hospital Organization Nagasaki Medical Center. Among patients who had been diagnosed with juvenile myoclonic epilepsy, those who received lacosamide as adjunctive therapy for refractory generalized tonic-clonic seizures for at least 2 years from January 2017 to December 2022, and who achieved seizure freedom or >50% seizure reduction in tonic-clonic seizures were included. The medical records and neurophysiological data of the patients were reviewed retrospectively. RESULTS: Four patients met the inclusion criteria. The mean age at the onset of epilepsy was 11.3 years (range 10-12), and the mean age of starting lacosamide was 17.5 years (range 16-21). All patients received two or more antiseizure medications prior to lacosamide. Three of four patients had seizure freedom for more than 2 years, and the one remaining patient had >50% seizure reduction for more than one year. Only one patient had recurrent myoclonic seizures after starting lacosamide. The mean lacosamide dose at the last visit was 425 mg/day (range 300-600). CONCLUSION: Adjunctive lacosamide therapy might be a treatment option for juvenile myoclonic epilepsy with generalized tonic-clonic seizures, which are not responsive to standard antiseizure medications.

The HCN1 p.Ser399Pro variant causes epileptic encephalopathy with super-refractory status epilepticus.

HCN1 is one of four genes encoding hyperpolarization-activated cyclic nucleotide-gated channels. The phenotypic spectrum associated with HCN1 variants ranges from neonatal developmental and epileptic encephalopathy to idiopathic generalized epilepsy. We report a Japanese patient with repetitive focal seizures and super-refractory status epilepticus since early infancy caused by a de novo HCN1 variant, NM_021072.4, c.1195T>C, p.(Ser399Pro). This variant might have a dominant-negative effect on channel function, leading to severe epileptic encephalopathy.