CDKL5 and ARX mutations are not responsible for early onset severe myoclonic epilepsy in infancy.
BACKGROUND
Severe myoclonic epilepsy of infancy (SMEI) or Dravet syndrome (DS) is a distinctive epilepsy syndrome often associated with de novo mutations in the SCN1A gene. However, 25-30% patients with SMEI/DS are negative for SCN1A mutation screening, suggesting that other molecular mechanisms may account for these disorders. Given the overlapping and heterogeneous clinical features of CDKL5- and ARX-related epilepsies and SMEI/DS, we postulated that CDKL5 mutations in females and ARX mutations gene in males may be associated with early onset seizures forms of SMEI/DS.


METHODS
Twenty-eight patients with early onset SMEI/DS before 6 months negative for SCN1A mutational screening were selected and screened for mutations in the ARX gene in males (n=14) or the CDKL5 gene in females (n=14).


RESULTS
No mutations in either gene were found except one intronic variation of uncertain pathogenicity in the CDKL5 gene. All patients started seizures at mean age of 3.48 months. Thirteen patients had familial history of epilepsy or febrile seizures. Patients evolved toward refractory epilepsy with generalized tonic clonic seizures (18/28) and myoclonia (23/28) and severe neurological impairment with autistic features (13/28), ataxia (14/28) and spasticity (5/28). No patient ever exhibited infantile spasms, dystonia, or Rett-like features.


CONCLUSIONS
Our results illustrate that mutation screening of ARX and CDKL5 is not effective in patients selected on the basis of clinical signs associated to early onset SMEI/DS. In addition, they might reflect that other phenotypic features associated with CDKL5 mutations (Rett-like features, infantile spasm) or ARX mutations (dystonia, spasticity) are more distinctive.
Nabbout
Rima
R
Service de Neurologie Pediatrique, hôpital Necker Enfants Malades, APHP, Université Paris Descartes, Paris, France.
Depienne
Christel
C
Chipaux
Mathilde
M
Girard
Benoit
B
Souville
Isabelle
I
Trouillard
Oriane
O
Dulac
Olivier
O
Chelly
Jamel
J
Afenjar
Alexandra
A
Héron
Delphine
D
Leguern
Eric
E
Beldjord
Cherif
C
Bienvenu
Thierry
T
Bahi-Buisson
Nadia
N
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004831:Epilepsies, Myoclonic / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005838:Genotype; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D008297:Male; D009154:Mutation; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D003294:Seizures, Febrile / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D055815:Young Adult
C469264:ARX protein, human; D018398:Homeodomain Proteins; D014157:Transcription Factors; D017346:Protein Serine-Threonine Kinases; C114482:CDKL5 protein, human