GTR Home > Conditions/Phenotypes > Hyperekplexia hereditary

Disease characteristics

Excerpted from the GeneReview: Hyperekplexia
Hereditary hyperekplexia (HPX) is characterized by generalized stiffness immediately after birth that normalizes during the first years of life; excessive startle reflex (eye blinking and a flexor spasm of the trunk) to unexpected (particularly auditory) stimuli; and a short period of generalized stiffness following the startle response during which voluntary movements are impossible. Exaggerated head-retraction reflex (HRR) consisting of extension of the head followed by violent flexor spasms of limbs and neck muscles elicited by tapping the tip of the nose is observed in most children. Other findings include periodic limb movements in sleep (PLMS) and hypnagogic (occurring when falling asleep) myoclonus. Sudden infant death (SIDS) has been reported. Intellect is usually normal; mild intellectual disability may occur.

Available tests

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Associated genes

Clinical features

  • Apnea
  • Umbilical hernia
  • Hypertonia
  • Frequent falls
  • Hypokinesia
  • Seizure
  • Aspiration
  • Inguinal hernia
  • Myoclonus
  • Exaggerated startle response
  • Hip dislocation
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