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


CONCLUSIONS
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.
Department of Ophthalmology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
H
H
Du
S R
SR
Grob
L
L
Zhao
J
J
Lee
M
M
El-Sahn
G
G
Hughes
J
J
Luo
K
K
Schaf
Y
Y
Duan
J
J
Quach
X
X
Wei
P
P
Shaw
D
D
Granet
K
K
Zhang
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D002675:Child, Preschool; D018118:Chloride Channels / Q000235:genetics; D004948:Esotropia / Q000175:diagnosis / Q000235:genetics*; D005133:Eye Movements / Q000502:physiology; D005141:Eyelid Diseases / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D009224:Myotonia Congenita / Q000175:diagnosis / Q000235:genetics*; D062553:NAV1.4 Voltage-Gated Sodium Channel; D010375:Pedigree; D016133:Polymerase Chain Reaction; D015222:Sodium Channels / Q000235:genetics*; D014792:Visual Acuity / Q000502:physiology
C086321:CLC-1 channel; D018118:Chloride Channels; D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human; D015222:Sodium Channels