Myotonia congenita with strabismus in a large family with a mutation in the SCN4A gene

• Published in: Eye (London) Vol. 26; no. 8; pp. 1039 - 1043
• Main Authors: Du, H, Grob, S R, Zhao, L, Lee, J, El-Sahn, M, Hughes, G, Luo, J, Schaf, K, Duan, Y, Quach, J, Wei, X, Shaw, P, Granet, D, Zhang, K
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2012; Nature Publishing Group
• Subjects: 631/208/2489/144; 692/1807/1482; 692/699/375/374; 692/700/139; Adult; Aged; Aged, 80 and over; Base Sequence; Biological and medical sciences; Child, Preschool; Chloride Channels - genetics; Clinical Study; Diseases of striated muscles. Neuromuscular diseases; Esotropia - diagnosis; Esotropia - genetics; Eye Movements - physiology; Eyelid Diseases - diagnosis; Eyelid Diseases - genetics; Female; Humans; Laboratory Medicine; Male; Medical sciences; Medicine; Medicine & Public Health; Miscellaneous; Molecular Sequence Data; Mutation; Myotonia Congenita - diagnosis; Myotonia Congenita - genetics; NAV1.4 Voltage-Gated Sodium Channel; Neurology; Oculomotor disorders; Ophthalmology; Pedigree; Pharmaceutical Sciences/Technology; Polymerase Chain Reaction; Sodium Channels - genetics; Surgery; Surgical Oncology; Visual Acuity - physiology; myotonia congenita; genetics; strabismus; esotropia; Esotropia; Nervous system diseases; Neuromuscular diseases; Family study; Myotonia; Eye disease; Gene; Family environment; Genetics; Mutation; Ophthalmology; Oculomotor syndrome
• ISSN: 0950-222X; 1476-5454
• DOI: 10.1038/eye.2012.80

Background/Aims To determine the genetic basis of myotonia congenita (MC) and strabismus in a large Caucasian family. Methods Seven patients making up four generations of a family with MC and strabismus were recruited. All patients had at least one standard ophthalmic examination, including best-corrected visual acuity, refraction, and ocular motility measurements. CLCN1 and SCN4A genes were sequenced and analysed for mutations. Results Five out of the seven family members were diagnosed with MC by clinical history and electromyography. Ophthalmic history and exam revealed eyelid myotonia and strabismus. All patients with MC were diagnosed with strabismus between the ages of 3 and 6 and required surgical restoration of ocular alignment. Sequencing results revealed a c. 1333G>A; p. Val445Met mutation in the SCN4A gene. Conclusion There are few reports describing eyelid myotonia and strabismus in patients diagnosed with MC. We found significant ocular involvement in a family with a mutation in SCN4A . Future studies may confirm that MC with significant ocular involvement can be used to direct genetic analysis.