SNP Shot: Genomic Insights

Benign familial neonatal seizures (BFNS) is a disorder where newborn infants experience repeated seizures. These seizures typically start around the third day of life and usually resolve within one to four months. The seizures can be either focal, affecting only one side of the brain, or generalized, affecting both sides. Often, BFNS involves generalized tonic-clonic seizures, also known as grand mal seizures. These seizures affect the entire body and involve two phases: tonic seizures, characterized by stiffening of the muscles, and clonic seizures, characterized by jerking movements. In BFNS, seizure episodes usually start with muscle stiffness and pauses in breathing (apnea) before progressing to clonic jerking.

An electroencephalogram (EEG), a test that measures the brain's electrical activity, can sometimes detect abnormalities that suggest a risk for seizures, even when no seizure is occurring. However, in infants with BFNS, EEG results are often normal. In some cases, a specific EEG abnormality called the theta pointu alternant pattern may be observed. By the age of two, most individuals with BFNS who initially had abnormal EEG readings will have normal EEG results.

Typically, seizures are the primary symptom of BFNS, and most individuals with the condition develop normally. However, some individuals may develop intellectual disability, which becomes apparent in early childhood. A small proportion of individuals with BFNS also experience myokymia, characterized by involuntary rippling muscle movements. Furthermore, in approximately 15 percent of individuals with BFNS, epilepsy may recur later in life, even after the initial BFNS-related seizures have stopped. The age of onset for this later-onset epilepsy varies.

Inheritance:

BFNS follows an autosomal dominant inheritance pattern. This means that only one copy of the mutated gene in each cell is enough to cause the condition. Most individuals with BFNS inherit the mutated gene from an affected parent. However, some cases arise from new mutations in the KCNQ2 gene, occurring in individuals with no family history of BFNS.