Familial neonatal convulsions
| Benign familial neonatal epilepsy | |
|---|---|
| Classification and external resources | |
| Specialty | neurology |
| OMIM | 121200 121201 608217 |
| DiseasesDB | 33689 |
| eMedicine | neuro/32 |
| MeSH | D020936 |
Benign familial neonatal seizures (BFNS), formerly called benign familial neonatal convulsions (BFNC), is a rare autosomal dominant inherited form of seizures. It manifests in newborns, normally within the first 7 days of life, as tonic-clonic seizures. Infants are otherwise normal between attacks and develop without incident. Attacks normally spontaneously cease within the first 15 weeks of life. Lifetime susceptibility to seizures is increased, as 16% of those diagnosed with BFNE earlier in life will go on to have seizures versus a 2% lifetime risk for the general population. There are three known genetic causes of BFNE, two being the voltage-gated potassium channels KCNQ2 (BFNC1) and KCNQ3 (BFNC2) and the third being a chromosomal inversion (BFNC3). There is no obvious correlation between most of the known mutations and clinical variability seen in BFNE.
The only sign of BFNE are seizures, generally tonic-clonic, which occur within the first week of life. Seizures often begin as apnea, cyanosis, and hypertonia and last less than 1 minute.
People with BFNE are not more likely to develop epileptic seizures later in life.
The most prevalent known cause of BFNE is mutation of KCNQ2, a gene encoding a voltage-gated potassium channel (KV7.2). There are at least 35 such mutations, see Table 1, primarily located in the voltage sensitive S4 segment through the C-terminus. Of these mutations, 5 are nonsense mutations, 13 are missense mutations and 11 cause a frameshift in the coding sequence. There are also 5 splice variants, one of which has been characterized at the protein level and leads to a nonsense mutation. Finally, there is one large deletion that removes much of the carboxy-terminus of the channel.
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