Genotype-phenotype correlations in hyperekplexia: apnoeas, learning difficulties and speech delay

Area of Science:

• Genetics
• Neuroscience
• Pediatrics

Background:

• Congenital hyperekplexia is a rare neuromotor disorder affecting glycinergic neurotransmission.
• Three major genes (GLRA1, GLRB, SLC6A5) are implicated, all influencing glycine receptor or transporter function.
• The disorder presents with characteristic stiffness, startles, and potentially life-threatening apnoea attacks.

Purpose of the Study:

• To analyze the genetic basis and clinical presentation of congenital hyperekplexia.
• To correlate specific gene mutations with clinical phenotypes, including developmental outcomes.
• To evaluate the efficacy of clonazepam and recommend diagnostic and counseling strategies.

Main Methods:

• Retrospective analysis of 97 individuals with genetically confirmed congenital hyperekplexia.
• Genetic testing for mutations in GLRA1, GLRB, and SLC6A5.
• Clinical data review including symptom onset, treatment response, and developmental milestones.

Main Results:

• Mutations in GLRA1, SLC6A5, and GLRB were identified in 97 cases, with GLRA1 being the most common.
• All gene-positive cases presented neonatally; clonazepam was effective in 95%.
• SLC6A5 and GLRB mutations were associated with higher rates of infantile apnoeas and developmental delay, particularly speech acquisition.

Conclusions:

• Congenital hyperekplexia is primarily a recessive disorder, though dominant forms exist.
• Early genetic diagnosis is crucial for timely treatment with clonazepam.
• Specific gene mutations predict phenotype severity and developmental challenges, guiding genetic counseling and management.