Progressive myoclonic epilepsy-6 is an autosomal recessive neurologic disorder characterized by onset of ataxia in the first years of life, followed by action myoclonus and seizures later in childhood, and loss of independent ambulation in the second decade. ... Progressive myoclonic epilepsy-6 is an autosomal recessive neurologic disorder characterized by onset of ataxia in the first years of life, followed by action myoclonus and seizures later in childhood, and loss of independent ambulation in the second decade. Cognition is not usually affected, although mild memory difficulties may occur in the third decade (summary by Corbett et al., 2011). For a discussion of genetic heterogeneity of progressive myoclonic epilepsy, see EPM1A (254800).
Corbett et al. (2011) reported 6 patients, including 2 sibs, with early childhood onset of progressive myoclonic epilepsy. One child was born of consanguineous Australian parents, and the others were of German or Dutch descent. The phenotype was ... Corbett et al. (2011) reported 6 patients, including 2 sibs, with early childhood onset of progressive myoclonic epilepsy. One child was born of consanguineous Australian parents, and the others were of German or Dutch descent. The phenotype was homogeneous: patients developed progressive ataxia between ages 1 and 3 years, followed by action myoclonus between ages 6 to 10 years. Most became wheelchair-bound with areflexia in their mid-teens, although 1 patient became wheelchair-bound at age 24. A few patients had tremor and fine motor problems. All had seizures of some sort, either drop attacks, absence seizures, or tonic-clonic seizures. EEG showed active generalized spike and wave and polyspike patterns, as well as photosensitivity. All patients developed scoliosis, 2 had syndactyly, and most had increased serum creatine kinase. Cognition was normal in all, although 2 patients showed subtle memory difficulties in the third decade.
In 5 unrelated patients with progressive myoclonic epilepsy-6, Corbett et al. (2011) identified a homozygous loss-of-function mutation in the GOSR2 gene (G144W; 604027.0001). Haplotype analysis indicated a founder effect, most likely of European origin, approximately 3,600 years ago. ... In 5 unrelated patients with progressive myoclonic epilepsy-6, Corbett et al. (2011) identified a homozygous loss-of-function mutation in the GOSR2 gene (G144W; 604027.0001). Haplotype analysis indicated a founder effect, most likely of European origin, approximately 3,600 years ago.