LGI1 Gene Change Linked To Severe Infant Epilepsy

What was studied

This report describes one infant girl with very severe epilepsy and developmental problems. She was born to consanguineous parents and began having seizures in the neonatal period. Her seizures were hard to control, including recurrent multifocal seizures and refractory status epilepticus, despite multiple antiseizure medications and a ketogenic diet.

Doctors used whole-exome sequencing and found that she had a homozygous pathogenic variant in the LGI1 gene. The report also notes that her unaffected parents and 2 other affected family members carried the same variant in only one copy (heterozygous state). The authors compared this pattern with what is already known about LGI1, which is usually linked to autosomal-dominant lateral temporal lobe epilepsy and typically benign, pharmacoresponsive seizures in heterozygous carriers.

What they found

The main finding is that having two altered copies of LGI1 may be linked to a much more severe condition than the better-known LGI1-related epilepsy seen in people with one altered copy. In this infant, the homozygous LGI1 variant was associated with neonatal-onset, drug-resistant epilepsy, profound developmental delay, and death at 7 months of age.

The authors suggest that this case broadens the known range of LGI1-related disease from a usually milder, often pharmacoresponsive epilepsy to a possible developmental and epileptic encephalopathy when both gene copies are affected. They also mention animal model data that support an important role for LGI1 in neurodevelopment and seizure control.

Limits of the evidence

This is a single case report, so it cannot prove that the LGI1 variant alone caused all of the child's symptoms or show how often this happens. Results from one infant may not apply to other children or families.

The abstract gives limited detail about the other family members, so it is hard to compare their symptoms directly. It also does not provide broader patient data or functional testing in this child beyond the genetic result and reference to animal models.

For families and caregivers

For families, this report suggests that LGI1 changes may sometimes be linked to much more severe epilepsy when a child inherits two altered copies, especially in consanguineous families where both parents may carry the same variant. It may help explain why genetic testing and genetic counseling can matter in severe early-onset epilepsy.

Still, this report does not mean every child with an LGI1 variant will have this course. Most evidence here comes from one infant, so families should view it as an important clue rather than a final answer about all LGI1-related epilepsy.

What to watch next

Stronger evidence would come from more children with homozygous LGI1 variants and additional studies clarifying how these variants relate to brain development and seizure control.

Terms in this summary

homozygous

Having the same gene change in both copies of a gene, one inherited from each parent.

heterozygous

Having a gene change in only one of the two copies of a gene.

pathogenic variant

A gene change judged to be disease-causing based on available evidence.

developmental and epileptic encephalopathy

A severe group of childhood-onset epilepsy disorders associated with developmental impairment.

status epilepticus

A seizure that lasts too long or repeated seizures without recovery in between; this is a medical emergency.

whole-exome sequencing

A genetic test that looks at the parts of genes that contain instructions for making proteins.

consanguineous

Describes parents who are biologically related, such as cousins.

ketogenic diet

A high-fat, very low-carbohydrate diet sometimes used to help control hard-to-treat seizures.