PRRT2 Gene Changes Linked To Seizures And Movement Disorders

What was studied

This was a retrospective case series from one children's hospital in China. It included 21 pediatric patients with PRRT2-related disorders: 14 with benign familial infantile epilepsy (BFIE), 2 with non-BFIE epilepsy, 4 with paroxysmal kinesigenic dyskinesia (PKD), and 1 with hemiplegic migraine (HM). The group included 12 boys and 9 girls.

The researchers reviewed electronic medical records and used family-based whole-exome sequencing to identify PRRT2 variants. Variants were classified using ACMG guidelines. They also used in silico prediction tools for a novel missense variant and functional analysis to examine the effect of one intronic variant on mRNA splicing.

What they found

Most of the identified variants were frameshift mutations, and the most common was c.649dupC. The phenotypes appeared at different ages in this cohort: BFIE in infancy, PKD in childhood or adolescence, and HM in adolescence. Most patients were reported to respond well to sodium channel blockers.

The study also described 2 notable variants. One was a novel heterozygous missense variant, c.811C > T (p.Leu271Phe), identified in a patient with drug-resistant focal epilepsy; in silico tools predicted it to be damaging. The other was an intronic variant, c.880-34G > A, which functional analysis showed led to abnormal mRNA splicing and a premature termination codon. The authors state that these findings expand the known PRRT2 mutational spectrum and suggest that PRRT2-related disorders are not invariably associated with a benign prognosis.

Limits of the evidence

This was a small retrospective case series from a single hospital, so the findings may not apply to all children with PRRT2-related disorders. Because it relied on existing records, some clinical details may have been limited. The study describes patterns in this cohort but does not fully establish genotype-phenotype correlations, especially for rare variants.

The novel missense variant was supported by in silico prediction and a single patient's clinical presentation in the abstract, so additional evidence from more patients or functional studies would strengthen interpretation. The abstract reports treatment response in general terms, without detailed comparisons between medicines or long-term outcomes.

For families and caregivers

For families, this study suggests that PRRT2-related conditions can appear in different ways over time, not only as infant seizures. In this cohort, some patients had later movement symptoms such as PKD, and one had hemiplegic migraine. The study also reports that many patients responded well to sodium channel blockers, although one patient with a novel missense variant had drug-resistant epilepsy.

The paper supports the value of genetic evaluation in understanding a child's diagnosis and possible range of PRRT2-related symptoms. Still, this study cannot predict what will happen for any one child, and the evidence comes from a small group at one center.

What to watch next

Larger multi-center studies with longer follow-up and additional functional testing of rare PRRT2 variants could help clarify genotype-phenotype correlations and treatment patterns.

Terms in this summary

PRRT2 gene

A gene associated with several paroxysmal neurologic disorders, including some infant epilepsies and movement disorders.

BFIE

Benign familial infantile epilepsy, a seizure disorder that begins in infancy and is often inherited.

PKD

Paroxysmal kinesigenic dyskinesia, brief episodes of abnormal movements that are often triggered by sudden movement.

HM

Hemiplegic migraine, a rare type of migraine that can include temporary weakness on one side of the body.

frameshift mutation

A DNA change that shifts how the genetic code is read and often leads to an abnormal or shortened protein.

missense variant

A DNA change that replaces one amino acid in a protein with another.

intronic variant

A DNA change in a non-coding region of a gene that can still affect gene processing.

splicing

The process by which RNA is cut and joined into its mature form before protein production.