Benign neonatal epilepsy family (Benign familial neonatal seizures -BFNS-) - KCNQ2 and KCNQ3 genes.
Benign familial neonatal epilepsy the (BFNS) is characterized alteration, epilepsy in infants. Seizures appear about 3 days of life and usually disappear within 1-4 months. Seizures may involve only one side of the brain (focal seizures) or both sides (generalized seizures). Many affected infants have tonic-clonic seizures. This type of seizure affects both sides of the brain and affects the entire body, causing muscle stiffness, seizures and loss of consciousness.
Measurements by an electroencephalogram (EEG) may indicate a risk of seizures. However, children with BFNS usually have normal EEG readings. In some affected individuals, the EEG shows a specific abnormality called theta-pointu alternating pattern. At 2 years, most affected individuals who had EEG abnormalities have normal EEG reading.
Usually, seizures are the only symptom of BFNS, and most of those affected develop normally. However, some affected individuals with an intellectual disability becomes evident in early childhood. A small percentage of people with BFNS also have a condition called mioquimia. In addition, around 15% of people with BFNS, epilepsy recurs later in life after seizures related to the disease disappear. The age when epilepsy begins is variable.
Benign familial neonatal epilepsy the (BFNS) is due to mutations in the KCNQ2 gene, located on the long arm of chromosome 20 (20q13.3) and in the KCNQ3 gene, located on the long arm of chromosome 8 (8q24). Mutations in the KCNQ2 gene are much more common cause of the disease that mutations in the gene KCNQ3.
These genes encode proteins that interact to form potassium channels, potassium ion transporting between the inside and outside of cells, and play a key role in the ability of a cell to generate and transmit electrical signals. Channels formed with KCNQ2 and KCNQ3 protein active in neurons, where potassium ions are transported to the outside of cells. These channels carry a particular type of electrical signal called M - current, which prevents a neuron continue to send signals to other neurons to ensure that they are not constantly active. Potassium channels are composed of several subunits. Each channel contains four alpha subunits that form the pores through which potassium ions move. Four alpha subunits KCNQ2 gene may constitute a channel. However, the alpha subunits KCNQ2 may also interact with alpha subunits encoded from the KCNQ3 gene to form a functional channel potassium, and these channels carry a much stronger M current.
They have identified 60 mutations in the KCNQ2 gene and at least 3 mutations in the KCNQ3 gene in families with familial neonatal epilepsy benign (BFNS). Sometimes, the mutated protein never reaches the cell surface to form a channel, or the channel may be located in the wrong part of the neuron. Alternatively, the channel formed from the mutated protein does not work. As a consequence of these mutations, the current M is reduced or altered, which leads to excessive excitability of neurons. It is likely that current reduction M 25% is sufficient to cause the disease. The seizures occur when neurons in the brain are abnormally excited. It is unclear why the seizures stop around 4 months old. It is likely that potassium channels formed from the KCNQ2 and KCNQ3 proteins play an important role in preventing excessive excitability of neurons in newborns. About 70% of people with BFNS have a mutation in the gene KCNQ2 or KCNQ3 gene. It is working to identify other mutations of genes involved in this disease.
This disease is inherited as an autosomal dominant, which means that a copy of the altered gene in each cell is sufficient for alteration is expressed. In most cases, an affected person inherits the mutation from an affected parent. A few cases are due to new mutations in the KCNQ2 gene. These cases occur in people with no history of disease in your family.
Tests in IVAMI: in IVAMI perform detection of mutations associated with familial neonatal epilepsy benign (BFNS), by complete PCR amplification of exons KCNQ2 and KCNQ3 the genes, respectively, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).