[A pedigree of hereditary hyperekplexia].

A 31-year old women presented with excessive startle reflex and frequent falls. Her startle reflex is induced by slight stimuli which are not problematic in most people. Soon after her startle reflex is evoked, generalized muscle stiffness occurs. She becomes rigid and falls down without loss of consciousness. Because she cannot protect herself when she is startled and falls, she has repeatedly bruised her head and face. The pedigree includes her father and two sisters with similar symptoms. Gene analysis revealed GLRA1 mutation, and she was diagnosed with hereditary hyperekplexia (HPX). Symptoms improved with clonazepam 1 mg/day. HPX patients live with severe anxiety about frequent falls and sometimes suffer serious injury, such as cerebral concussion or bone fracture. Although HPX might sometimes be underestimated, accurate diagnosis is very important for effective treatment.