Table 1.
Clinical presentations in patients with the four mutations.
| Genotype in patients | c.740C > A (S247X)42 | c.740C > G (S247W)41 | c.740C > T (S247L) | c.853 C > A (P285T) |
|---|---|---|---|---|
| Pattern of inheritance | Inherited, autosomal dominance | De novo | De novo | De novo |
| Functional domain | S5 | S5 | S5 | Pore domain |
| Family history | + (5 affected family members) | No | No | No |
| First seizure day | Day 5 | Day 3 | Day 3 | Day 2 |
| Seizure frequency before drug control | + | +++ | +++ | +++ |
| Antiepileptic drugs | PB | Intravenous PB, PHT, oral pyridoxine, PB, and SAB | Intravenous PB, PHT then oral PB, SAB, CLN | Intravenous PB, PHT then oral PB, SAB, CLN, OXC |
| Age when seizure-free | 6 months | No remission of seizures | Partial remission of seizures at 4 months, with recurrent febrile seizures | Partial remission of seizures at 2 months |
| Seizure types | Bicycling of legs and arms, apnea | Multifocal with left or right head deviation and upper and lower limb involvement | Generalized tonic | Generalized tonic |
| Initial EEG | Central sharp waves or spikes | Burst-suppression pattern | Burst-suppression pattern | Burst-suppression pattern |
| MRI/ CT | Normal | Normal MRI at 18 days and normal third CT scan at 30 days | Basal ganglion | Thin corpus callosum |
| Neurodevelopmental outcomes | Unremarkable | Poor at 2 year and 5 months: head control and social smiling but inability to sit without support, muscle hypotonia, dystonic features | Poor at 3 years: inability to sit without support, inability to walk, lack of language production, severe cognitive disability | Poor at 2 years and 4 months: inability to sit without support, inability to walk, lack of language production, severe cognitive disability |
PHT, phenytoin; OXC, oxcarbazepine; TOP, topiramate; PB, phenobarbital; SAB, vigabatrin; CLN, clonazepam; MRI, magnetic resonance imaging; CT, computed tomography; EEG, electroencephalography; ++ +, daily; ++, weekly; +, less than weekly; ADHD, attention deficit and hyperactivity; Dev. Del./Int. Dis., Developmental delay/intellectual disability. The sequence data of each patient were checked against the GenBank reference sequence and version number of KCNQ2 gene (NM_172107.3).