Myotonia congenita is a rare muscular disorder with autosomal dominant or autosomal recessive inheritance, and is characterized by painless myotonia. A 44-year-old mother presented at our clinic with a son and a daughter, all sharing the same complaints of difficulty in relaxing their hands and beginning to walk, and spasms during chewing. The family had also another 16-year-old daughter, but she had no such complaints. The mother reported that her father and 2 sisters had the same disease, but that her brother was healthy. Their pedigree analysis revealed that the disease was present for 3 generations and had an autosomal dominant trait. During the neurologic examination of cases, action and percussion myotonia were observed in the hand, arm, and leg muscles. Her asymptomatic daughter had also generalized myotonia. Needle electromyography of all cases revealed generalized myotonic discharges in the muscles examined. The cases are presented due to the presence of MC in 3 generations of the family. This case study reveals that EMG studies are useful in determining myotonic disorders in asymptomatic cases.

Myotonia congenita is a rare muscular disorder with autosomal dominant or autosomal recessive inheritance, and is characterized by painless myotonia. A 44-year-old mother presented at our clinic with a son and a daughter, all sharing the same complaints of difficulty in relaxing their hands and beginning to walk, and spasms during chewing. The family had also another 16-year-old daughter, but she had no such complaints. The mother reported that her father and 2 sisters had the same disease, but that her brother was healthy. Their pedigree analysis revealed that the disease was present for 3 generations and had an autosomal dominant trait. During the neurologic examination of cases, action and percussion myotonia were observed in the hand, arm, and leg muscles. Her asymptomatic daughter had also generalized myotonia. Needle electromyography of all cases revealed generalized myotonic discharges in the muscles examined. The cases are presented due to the presence of MC in 3 generations of the family. This case study reveals that EMG studies are useful in determining myotonic disorders in asymptomatic cases.