Isolated eyelid closure myotonia in two families with sodium channel myotonia.
Sodium channelopathies (NaCh), as part of the non-dystrophic myotonic syndromes (NDMs), reflect a heterogeneous group of clinical phenotypes accompanied by a generalized myotonia. Because of recent availability of diagnostic genetic testing in NDM, there is a need for identification of clear clinical genotype-phenotype correlations. This will enable clinicians to distinguish NDMs from myotonic dystrophy, thus allowing them to inform patients promptly about the disease, perform genetic counseling, and orient therapy (Vicart et al. Neurol Sci 26:194-202, 2005). We describe the first distinctive clinical genotype-phenotype correlation within NaCh: a strictly isolated eyelid closure myotonia associated with the L250P mutation in SCN4A. Using clinical assessment and needle EMG, we identified this genotype-phenotype correlation in six L250P patients from one NaCh family and confirmed this finding in another, unrelated NaCh family with three L250P patients.
Stunnenberg
B C
BC
Department of Neurology, Neuromuscular Centre Nijmegen, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Ginjaar
H B
HB
Trip
J
J
Faber
C G
CG
van Engelen
B G
BG
Drost
G
G
D000328:Adult; D000368:Aged; D001483:Base Sequence; D053447:Channelopathies / Q000235:genetics*; D004252:DNA Mutational Analysis; D005143:Eyelids / Q000033:anatomy & histology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009222:Myotonia / Q000235:genetics* / Q000503:physiopathology; D062553:NAV1.4 Voltage-Gated Sodium Channel; D010375:Pedigree; D015222:Sodium Channels / Q000235:genetics*; D055815:Young Adult
D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human; D015222:Sodium Channels