SCN1A mutation mosaicism in a family with severe myoclonic epilepsy in infancy.
OBJECTIVE
To investigate the genetic background of familial severe myoclonic epilepsy in infancy (SMEI) cases.


METHODS
We performed mutation analyses of the sodium-channel gene SCN1A in two Japanese brothers with clinical features of SMEI and their parents, who had no history of febrile and epileptic seizures.


RESULTS
Each patient showed nucleotide changes (c.[730G>T; 735G>T; 736A>T]) in the coding exon 6 of SCN1A that led to a truncation of the channel protein. Their father showed no mutations, but their mother showed the same mutation in a subpopulation of lymphocytes.


CONCLUSIONS
The maternal mosaicism explains the identical SCN1A mutations in the two brothers. This highlights the importance of investigating parental mosaicism even in sporadic SMEI cases.
Morimoto
Masafumi
M
Department of Pediatrics, Kyoto Prefectural University of Medicine, Kyoto, Japan. morimoto@koto.kpu-m.ac.jp
Mazaki
Emi
E
Nishimura
Akira
A
Chiyonobu
Tomohiro
T
Sawai
Yasuko
Y
Murakami
Aki
A
Nakamura
Keiko
K
Inoue
Ikuyo
I
Ogiwara
Ikuo
I
Sugimoto
Tohru
T
Yamakawa
Kazuhiro
K
D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004831:Epilepsies, Myoclonic / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D053503:Epithelial Sodium Channels / Q000235:genetics*; D005190:Family; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D009030:Mosaicism / Q000706:statistics & numerical data*; D009154:Mutation / Q000235:genetics*; D010290:Parents; D035781:Siblings
D053503:Epithelial Sodium Channels; C507045:SCNN1A protein, human