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Case Reports
. 2012 Aug;26(8):1039-43.
doi: 10.1038/eye.2012.80. Epub 2012 Jun 1.

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

H Du  1 , S R Grob, L Zhao, J Lee, M El-Sahn, G Hughes, J Luo, K Schaf, Y Duan, J Quach, X Wei, P Shaw, D Granet, K Zhang
Affiliations
Case Reports

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

H Du et al. Eye (Lond). 2012 Aug.

Abstract

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.

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Figures

Figure 1
Figure 1
Pedigree of a family affected by MC. The arrow points to the proband. Results from the genetic analysis of SCN4A are depicted beneath each investigated individual. Only affected individuals (I-2, II-1, III-2, III-3, and IV-1) harbour the V445M mutation.
Figure 2
Figure 2
The SCN4A sequencing results. Sequencing data show that a G–A transition in exon 9 (arrow) causes the V445M mutation in affected individuals (top). This alteration was absent in the unaffected individuals (bottom).
See this image and copyright information in PMC

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