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Abstract
IntroductionHereditary hyperekplexia is a neurological disorder characterized by excessive startle responses with violent jerking to noise or touch, stiffening of the trunk and limbs, clenching of the fists and attacks of a high-frequency trembling. Hyperekplexia has a heterogeneous genetic background with several identified causative genes and demonstrates both dominant and recessive inheritance. Mutations in the glycine receptor alpha 1 subunit gene occur in about 30 percent of hyperekplexia cases.Case presentationIn this study, we report the case of a Hungarian boy whose abnormal movements, muscle stiffness and convulsions were first noted when he was 4 days old. Neurological and electrophysiological investigation suggested the clinical diagnosis of hyperekplexia.ConclusionsDirect sequencing of the coding regions and the flanking introns of the glycine receptor alpha 1 subunit gene revealed a novel heterozygous missense mutation (c.211A/T, p.Ile71Phe). Genetic screening of our patient’s family revealed that the clinically unaffected parents and sister do not carry the mutation, suggesting that the identified sequence change is a de novo mutation. Since hyperekplexia can have severe consequences, including sudden infant death due to laryngospasm and cardiorespiratory failure, identification of the causative genetic alteration(s) of the disease is high priority. Such knowledge is necessary for prenatal diagnosis, which would allow informed family planning and greater parental sensitivity to hyperekplexia 1-associated risks.
Highlights
ConclusionsDirect sequencing of the coding regions and the flanking introns of the glycine receptor alpha 1 subunit gene revealed a novel heterozygous missense mutation (c.211A/T, p.Ile71Phe)
Hereditary hyperekplexia is a neurological disorder characterized by excessive startle responses with violent jerking to noise or touch, stiffening of the trunk and limbs, clenching of the fists and attacks of a high-frequency trembling
Hereditary hyperekplexia (HKPX, ORPHA3197) is an early-onset neurological disorder characterized by excessive startle responses with violent jerking to sudden, unexpected auditory or tactile stimuli [1,2]
Summary
We report the case of a Hungarian patient with hyperekplexia, a potentially fatal neurological disorder characterized by pronounced startle responses. Hyperekplexia has been linked to genetic alterations in genes involved in an inhibitory neurotransmitter, glycine neurotransmission [3,4] Both compound heterozygous patients and homozygous mutation carriers have been described in the literature for recessive forms of the disease [10]. A heterozygous missense mutation (c.211A/T, p.Ile71Phe) was detected in our patient in exon 3 of the GLRA1 gene, establishing the diagnosis of hyperekplexia 1 and suggesting that the mutation is an autosomal dominant form of the disease. It is interesting to note that previously reported missense mutations in this region (human p.Trp68Cys and p.Arg72His and murine p.Ala52Ser) are all associated with the recessive form of hyperekplexia 1, indicating the possibility that other undetected mutations might contribute to the clinical symptoms of our Hungarian patient.
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