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Hereditary Hyperekplexia


  • Trismus was the presenting feature, but she later developed hyperekplexia. Although most brainstem features resolved spontaneously, the hyperekplexia has persisted.[ncbi.nlm.nih.gov]
  • Due to its seizure-like presentation, it is usually misdiagnosed.[neurologyindia.com]
  • He currently is treated with clonazepam but still presents with moderate hypertonia of the limbs and jerks on nasal percussion.[jmg.bmj.com]
  • It occurs as part of anxiety, malingering, or fictitious movement disorder sudden in onset and quickly reaches peak severity and stops abruptly.[pediatricneurosciences.com]
  • […] tetrahydrobiopterin (BH4) (see this term), leading to decreased levels of neurotransmitters (dopamine, serotonin) and folate in cerebrospinal fluid, and causing neurological symptoms such as psychomotor delay, hypotonia, seizures, abnormal movements, hypersalivation[amp.pharm.mssm.edu]
High Arched Palate
  • He had minor dysmorphic features in the form of high arched palate, prominent ears, flat bridge of nose, small eyes, malformation of both hands in the form of undue separation of middle thumb and index finger with deformity, and scoliosis.[pediatricneurosciences.com]
Small Eyes
  • He had minor dysmorphic features in the form of high arched palate, prominent ears, flat bridge of nose, small eyes, malformation of both hands in the form of undue separation of middle thumb and index finger with deformity, and scoliosis.[pediatricneurosciences.com]
Neonatal Tetany
  • Differential diagnosis The differential diagnoses of hyperekplexia in the neonatal period include the congenital stiff-man syndrome, startle epilepsy, myoclonic seizures, neonatal tetany, and phenothiazine toxicity. 40 41 Hyperekplexia may also be misdiagnosed[pmj.bmj.com]
Facial Grimacing
  • grimacing with blinking, followed by involuntary movements of head flexion, hunching of shoulders, adduction of the arms, and flexion of the trunk and the knees, causing falling without a protective reaction. 9 10 It appears in infancy at the same time[pmj.bmj.com]
Psychiatric Symptoms
  • In addition to excessive startling, behavioral and/or psychiatric symptoms are observed.[ncbi.nlm.nih.gov]
Tic Disorder
  • Examples: Startle epilepsy Reticular and propriospinal myoclonus Tic disorders Subacute sclerosing panencephalitis Paraneoplastic syndromes Another startle-induced disorder is stiff person syndrome (SPS), characterized by progressive axial stiffness and[ncbi.nlm.nih.gov]
  • Autosomal dominant isolated somatotropin deficiency Triglyceride storage disease with ichthyosis Tourette Syndrome A tic disorder that is characterized by multiple physical (motor) tics and at least one vocal (phonic) tic present for more than a year.[amp.pharm.mssm.edu]
  • Following a startle reflex other responses may be seen, including echolalia and echopraxia.[ncbi.nlm.nih.gov]
  • It is mainly characterized by progressive spino-cerebellar ataxia, loss of proprioception, areflexia, and is associated with a marked deficiency in vitamin E.[amp.pharm.mssm.edu]
  • A myoclonic response to a tap on the nose, hyperreflexia with sustained clonus, hypertonia, jitteriness, and sleep myoclonus are the characteristic manifestations of the major form.[pediatricneurologybriefs.com]
  • They show myotonia clinically and electrophysiologically. [12] Gilles de la Tourette syndrome A syndrome which usually starts before 16 years of age with obsessions–compulsions, involuntary utterances, coprolalia, aggression, and repetitive motor activity[pediatricneurosciences.com]


  • We investigated him with neurometabolic workup, autoantibody profile for NMDA, VGKC, GAD, CK, and long loop reflexes which were noncontributory.[pediatricneurosciences.com]
  • Contributors: VBB carried out the workup, follow up, literature review and also drafted the manuscript. SBR was responsible for diagnosis, supervision and overall management. She will stand as the guarantor for the manuscript. Funding: None.[indianpediatrics.net]


  • Hypertonia was relieved and startle responses were milder following treatment with clobazam. At 18 month follow-up, an apnea monitor was discontinued, but clobazam treatment (0.2 mg/kg/daily) was still required. [ 1 ] COMMENT.[pediatricneurologybriefs.com]
  • Management and treatment Symptomatic treatment in adults involves clonazepam (1mg per day). In children lower doses are required. Vigabatrin is ineffective.[orpha.net]
  • Treatment with the proteasome blocker, lactacystin, significantly increased the accumulation of alpha1 mutants in intracellular membranes.[ncbi.nlm.nih.gov]
  • Drugs Used to Treat Hyperekplexia The following list of medications are in some way related to, or used in the treatment of this condition.[drugs.com]
  • Clonazepam, a gamma aminobutyric acid (GABA) receptor agonist, is the treatment of choice for hypertonia and apnoeic episodes. It, however, may not influence the degree of stiffness significantly.[pmj.bmj.com]


  • Prognosis In most patients, fear of falling and the toddling gait normalizes in adolescence.[orpha.net]
  • . • Treatment with clonazepam is effective with an eventual good prognosis. 1. Tohier C, Roze JC, David A, Veccierini MF, Renaud P, Mouzar D. Hyperekplexia or stiff-baby syndrome. Arch Dis Child 1991; 66: 460-461. 2. Giacoia Gp, Ryan SG.[indianpediatrics.net]


  • Etiology Mutations in the GLRA1 gene (5q32) are found in about 30% of patients with hereditary hyperekplexia (and a considerable number of patients without an obviously affected parent).[orpha.net]
  • In this article, the author details developments in etiology, genetics, and clinical manifestations. Pharmacological treatment of hyperekplexia with clonazepam is often lifesaving.[medlink.com]
  • […] the homozygous form in both the affected sisters, and absence of the variant in the homozygous form in unaffected family members. » Conclusion This case emphasizes the power of exome sequencing in the diagnosis of genetic disorders of heterogeneous etiologies[neurologyindia.com]


  • It reviews new findings, based on animal models, genetic studies and imaging, that have led to a deeper understanding of the clinical features, epidemiology, and pathogenesis of these disorders.[books.google.com]
  • Summary Epidemiology To date about 150 cases have been reported in the literature.[orpha.net]
Sex distribution
Age distribution


  • This evidence-based approach is essential for establishing the pathophysiological principles underlying the abnormal startle response.[doi.org]
  • Chung SK, Vanbellinghen JF, Mullins JG, Robinson A, Hantke J, Hammond CL, Gilbert DF, Freilinger M, Ryan M, Kruer MC, Masri A, Gurses C, Ferrie C, Harvey K, Shiang R, Christodoulou J, Andermann F, Andermann E, Thomas RH, Harvey RJ, Lynch JW, Rees MI: Pathophysiological[jmedicalcasereports.biomedcentral.com]


  • Author information 1 Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia. qshan@yahoo.com Abstract Hereditary hyperekplexia, or startle disease, is a neuromotor disorder caused mainly by mutations that either prevent[ncbi.nlm.nih.gov]
  • The timely diagnosis of hyperekplexia will allow families to take adequate preventive measures; moreover, prenatal diagnosis can be provided to families when mutation is identified in the proband. Financial support and sponsorship Nil.[neurologyindia.com]
  • Clonazepam may also help to prevent symptoms of HKPX. The GPHN and ARGHEF9 genes are associated with syndromic forms of HKPX.[invitae.com]
  • In some situations, determining the genetic cause of disease can provide clinically actionable guidance for treatment or prevention. CGI provides accurate science and services necessary to interpret disease causing mutations correctly.[genomicinterpretation.org]

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