Table 1.
Clinical phenotype of patients with MEF2C gene mutation.
| No. | P1 | P2 | P3 | P4 | P5 | P6 | P7 |
|---|---|---|---|---|---|---|---|
| Age | 5 years | 5 years 9 months | 4 years 4 months | 2 years 10 months | 6 years | 2 years 7 months | 2 years 5 months |
| Sex | F | F | F | F | F | M | F |
| Genetic defect | c.9A>T, (p.Arg3Ser) | c.78delT, (p.Phe26Leufs*3) | c.833_834insTT, (p.Leu278Phefs*1) | c.55-2(1VS2)A>G | C.44G>C, (p.R15P) | c.1A>G, (p.Met1Val) | c.3G>A, (p.Met1?) |
| Origin | Unknown | De novo | De novo | De novo | De novo | De novo | Unknown |
| Variation type | Missense | Frameshift | Frameshift | Splice site | Missense | Affecting the translation initiation site | Affecting the translation initiation site |
| Febrile seizure | + | + | + | + | - | + | - |
| Seizure type | Recurrent FS, GTC | Recurrent FS, GTC | Recurrent FS, absence | Recurrent FS, dystonic | GTC, IS | Recurrent FS, GTC | - |
| Age of seizure onset (months) | 1.5 years | 10 months | 8 months | 11 months | 6 months | 9 months | NA |
| ASM | LEV | LEV, OXC | LEV, VPA | OXC | VGB, LEV, VPA | VPA, OXC, TPM | NA |
| ASM response | Seizure free | Seizure free | Seizure free | Seizure free | Seizure free | No response | NA |
| Stereotypic movements | + | + | + | + | - | - | + |
| Poor hand skills | - | - | - | - | + | - | + |
| Delays in milestones | + | + | + | + | + | + | + |
| Independent sitting/age | 1 year | 1 year | 8–9 months | 1 year | - | 9 months but regressed | 2 years |
| Independent walking/age (months) | - | 2 years | 2 years | - | - | - | - |
| Infantile dystonia | Hypotonia | - | Hypotonia | Hypotonia | Hypotonia | Hypotonia | Hypotonia |
| Speech | - | - | - | - | - | - | - |
| Regression | - | + | - | + | - | + | - |
| Poor eye contact/autistic features | + | - | + | - | + | - | + |
| MRI | Frontal subarachnoid space enlargement | Normal | Delayed myelination | Normal | Delayed myelination | Small splenium of callosum | Normal |
| EEG | Bilateral temporal spike-slow waves | Bilateral temporal and occipital spike-slow waves | Generalized sharp-slow waves | Normal | Hypsarrhythmia | Left temporal and occipital slow waves | Left occipital 2–3 Hz sharp-slow waves in sleep |
FS, febrile seizure; GS, generalized seizures; GTC, generalized tonic-clonic seizures; IS, infantile spasms; LEV, levetiracetam; NA, not available; OXC, oxcarbazepine; PB, phenobarbital; PS, partial seizure; TPM, topiramate; VGB, vigabatrin; VPA, valproic acid; WMH, white matter hyperintensity.