Hyperekplexia, also known as stiff baby syndrome, is a rare neurological disorder characterized by abnormal startle responses and muscle stiffness. The condition primarily affects neonates and infants, though milder forms can persist into adulthood.

Clinical Features:

1. Neonatal Stiffness:

   • Generalized muscle rigidity, which can mimic increased tone, is often present at birth.

2. Excessive Startle Reflex:

   • Exaggerated startle responses to tactile, auditory, or visual stimuli are hallmark features.
   • Startle can trigger stiffening of the entire body (generalized tonic reflex), leading to falls or apnea.

3. Prolonged Apnea:

   • Severe startle episodes may cause apnea and cyanosis, which can be life-threatening.

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