Myoclonus-dystonia (M-D) is an autosomal dominantly inherited movement disorder with myoclonic jerks and dystonic contractions most frequently due to a mutation in the epsilon-sarcoglycan (SGCE, DYT11) gene.
An 8-year-old boy presenting with early onset, medically intractable, MDS due to a mutation in the epsilon-sarcoglycan gene (SGCE) underwent chronic bilateral stimulation of the globus pallidus internus, which eliminates both myoclonus and dystonia.
We report on the second M-D family in which several clinically affected epsilon-sarcoglycan gene (SGCE) mutation carriers have seizures in addition to myoclonus and dystonia, adding to the evidence that epilepsy and EEG abnormalities may form part of the phenotypic spectrum of the condition.
Patients with myoclonus and SGCE mutations also showed an improvement in action myoclonus (95%-100%) and in functional tests (50%-75%) according to the Unified Motor-Rating Scale.
Linkage analyses have shown that the genes for both these forms of myoclonus are closely linked to 21q22.3 DNA markers, suggesting that they are caused by mutations at the same locus (EPM1).
The aim of this article is to report on an early-onset AD patient associated with the rare pathogenic variant PSEN1 (Leu85Pro) presenting as a possible corticobasal syndrome with asymmetric limb apraxia, parkinsonian signs, and myoclonus.
Even though the vast majority of patients with EPM1 have a uniform genetic mutation, the actual size of the longer CSTB expansion mutation allele is likely to have a modulating effect on the age at disease onset, myoclonus severity, and cortical neurophysiology.
Presenilin 1 (PSEN1) gene mutations deterministic for Alzheimer's disease (AD) are associated with marked heterogeneity in clinical phenotype, with behavioral and psychiatric features, parkinsonism, myoclonus, epileptic seizures, spastic paraparesis, frontal behavioral changes suggestive of the phenotype of frontotemporal dementia, aphasia, and cerebellar ataxia being described as well as cognitive decline.
This family was characterized by relatively late onset (mean age at 50 years) in familial AD with PS-1 gene mutation and by absence of myoclonus, seizure or paratonia.
Cystatin B mutations are now known to account for both Mediterranean myoclonus and for "Baltic" myoclonus, described mainly from Finland, thus solving a long-term controversy and proving that these two disorders are one single disease entity.
Myoclonus and seizures were the most common additional neurological features; individuals with myoclonus (40 [47%] with PSEN1 mutations and 12 [33%] with APP mutations) were significantly more likely to develop seizures (p=0·001 for PSEN1; p=0·036 for APP), which affected around a quarter of the patients in each group (20 [24%] and nine [25%], respectively).
Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1S169L mutation in a case of familial AD with myoclonus and seizures.