Non-convulsive Status Epilepticus in SEMA6B-Related Progressive Myoclonic Epilepsy: A Case Report With Literature Review

Abstract

Progressive myoclonic epilepsy (PME) is a group of rare diseases characterized by progressive myoclonus, cognitive impairment, ataxia, and other neurologic deficits. PME has high genetic heterogeneity, and more than 40 genes are reportedly associated with this disorder. SEMA6B encodes a member of the semaphorin family and was first reported to cause PME in 2020. Herein, we present a rare case of PME due to a novel SEMA6B gene mutation in a 6-year-old boy born to healthy non-consanguineous Chinese parents. His developmental milestones were delayed, and he developed recurrent atonic seizures and myoclonic seizures without fever at 3 years and 11 months of age. He experienced recurrent myoclonic seizures, non-convulsive status epilepticus (NCSE), atonic seizures, and atypical absence seizures during the last 2 years. At different time points since onset, valproic acid, levetiracetam, piracetam, and clobazam were used to control the intractable seizures. Notably, NCSE was controlled by a combination of piracetam with clobazam and valproic acid instead of intravenous infusion of midazolam and phenobarbital. Due to the limited number of cases reported to date, the clinical description of our case provides a better understanding of the genotype–phenotype correlations associated with PME and indicate that piracetam may be effective against NCSE in patients with SEMA6B-related PME.

Negative Myoclonus: Neurophysiological Study and Clinical Impact in Progressive Myoclonus Ataxia

“…This is in line with the literature, as NM has been already described as part of the clinical phenotype in SEMA6B 37,38 and GOSR2 39 . Typically, these genetic disorders are associated with both PMA and PME phenotypes 14,16,38,40 . We could not detect NM in any patient with a genetic diagnosis exclusively associated with PMA, like ATM , KCNC3 , and SPTBN2 14,16 .…”

Discriminative features in White-Sutton syndrome: literature review and first report in Iran

“…The reported symptoms for the patient were Intellectual disability, sleep disturbance, dysmorphic features, hearing loss, vision problems, and congenital heart disease. Trio-based WES test was performed for the family and it revealed a frameshift mutation in POGZ gene (Duan et al ., 2023).…”

Progressive myoclonus epilepsies due to SEMA6B mutations. New variants and appraisal of published phenotypes

“…As far as we know, until now 29 patients with 22 different SEMA6B variants have been described, 18 of which within exon 17. 4,5,[7][8][9][10]12,13 SEMA6B variants include 5 missense, 5 nonsense, and 12 frameshift mutations (Table S1).…”

“…6 Twenty-nine patients have been reported so far, showing non-homogeneous phenotypes, ranging from developmental encephalopathy (DE) without epilepsy to developmental and epileptic encephalopathy (DEE) or PME. [7][8][9][10] With the aim of sharpening the distinctive features of the PME phenotype and to compare our observations with the available literature; here, we present the genetic and clinical characteristics of three adjunctive patients with PME, carrying different truncating SEMA6B pathogenetic variants, two of which are novel.…”

“…SEMA6B maps to chromosome 19p13.3; it encodes for a transmembrane protein member of the semaphorin family, playing a role in the early development of the central nervous system, affecting axonal guidance by interacting with neuropile receptors 6 . Twenty‐nine patients have been reported so far, showing non‐homogeneous phenotypes, ranging from developmental encephalopathy (DE) without epilepsy to developmental and epileptic encephalopathy (DEE) or PME 7–10 …”