Two mutations in the nicotinic acetylcholine receptor subunit A4 (CHRNA4) in a family with autosomal dominant sleep-related hypermotor epilepsy.

Langenbruch L¹, Biskup S², Young P³, Dräger B¹, Möddel G¹.

Sleep-related hypermotor epilepsy, or nocturnal frontal lobe epilepsy, as it was formerly called, is a focal epilepsy with mostly sleep-related seizures of hypermotor, tonic or dystonic semiology. Sleep-related hypermotor epilepsy may be attributed to a monogenetic cause with autosomal dominant inheritance. Mutations are described in different genes, including the genes for three subunits of the nicotinic acetylcholine receptor. We present a family with members over four generations exhibiting sleep-related hypermotor epilepsy. Genetic testing was available for three members from three generations, and revealed two variants in the alpha-4 subunit of the nicotinic acetylcholine receptor (one of them being novel) which are likely to be disease-causing. As these mutations were identified in cis configuration (on the same allele), we do not know whether one of the variants alone or a combination of the two is responsible for the pathogenicity.