Table 1 Genotypes and phenotypes of SYNGAP1 cohort
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 | – |