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Table 1 Genotypes and phenotypes of SYNGAP1 cohort

From: Phenotypic characterization of individuals with SYNGAP1 pathogenic variants reveals a potential correlation between posterior dominant rhythm and developmental progression

Subject Genetic mutation Age at diagnosis (months) Age at seizure onset EEG—intermittent rhythmic delta activity EEG—interictal epileptiform activity Cognitive/developmental impairment* MRI abnormalities
1 c. 1744G>T (p.E582X), c.2693C>G (p.S898C), c.2305C>G (p. L769 V) 32 23 Generalized spike-slow wave; evolved to multifocal epileptiform activity Moderate Mildly simplified frontal lobe gyral pattern
2 c.1652  T>C (p.L551P); chr6: 33406672 (NM_006772.2) 28 18 Occipital Generalized posterior dominant spike and wave discharges Severe T2 white matter subinsular, periatrial, and subcortical hyperintensities
3 c.427C>T (p.Arg143*) 45 24 Generalized and focal polyspike and wave and spike activity Moderate Small developmental venous anomalies
4 c.1154_1161del (p.S385 fs) 66 12 Generalized, maximal left hemisphere Generalized polyspike and wave and spike and wave activity Profound
5 c. 1167-1168del (p.G391 fs) 174 120 Generalized posterior dominant Generalized spike and wave discharges and multifocal spikes Profound
6 c.3190C>T (p. Q1064X), 3p12 loss 36 30 Generalized posterior dominant Generalized spike and wave discharges Profound
7 c.333del (p.L114Sfs20) 81 30 Generalized and multifocal spike and polyspike and wave discharges Mild
8 c.3233_3236del (p.V1078 fs) 80 12 Multifocal spikes Profound Nonspecific punctate white matter hyperintense foci
9 c.2561-2577del (p.840 fs) 65 17 Occipital and frontocentral Generalized and multifocal spike and polyspike and wave discharges Profound Nonspecific punctate white matter hyperintense foci
10 c.1861C>T (p.R621X) 90 48 Generalized spike and wave discharges Profound Chiari 1; thick corpus callosum
11 c. 2899 C>T (p.R967X) 36 37 Posterior and left mid-temporal Generalized posterior dominant spike and wave discharges Profound Chiari 1
12 c.2916delT (p.D974Tfs*103) 108 103 Right temporo-occipital Generalized and focal right occipital spikes Severe
13 c.3718C>T (p.R1240X) 55 62 Parieto-occipital bilateral Generalized spikes and polyspikes; focal left occipital spikes Severe T2 hyperintensities in bilateral centrum semiovale
14 c.2438delT (p.L813Rfs*23) 67 24 Generalized posterior dominant spike and wave discharges Severe
15 c.2916delT (p.D974Tfs*103) 60 24 Posterior bilateral Moderate
  1. *Based on approximate standard scores for Full-Scale Developmental Quotient: mild developmental/intellectual disability (DD/ID) 50–69; moderate DD/ID 35–49; severe DD/ID 20–34; profound DD/ID < 20