The recessive progressive myoclonic epilepsy syndrome is characterised by myoclonus and seizures including myoclonic, tonic-clonic and focal seizure types. Onset is between 1 and 7 years. In some affected individuals early ataxia and intention tremor are noted. Bulbar myoclonus causes significant dysarthria. Microcephaly was not a feature. Neuroimaging demonstrated a structurally normal brain although cerebral and cerebellar atrophy were reported.
The dominant severe microcephaly syndrome is characterised by global developmental delay and intellectual disability varying from mild to severe. Progressive microcephaly, with measurements ranging from -3.6 to -12 SD, was present in most affected individuals. Seizures were present in about half of all affected individuals. In some affected individuals, short stature was noted. In the most severely affected individuals, severe hypotonia, visual impairment, scoliosis and feeding problems were present. Minor dysmorphic features were noted in some, but no characteristic pattern has emerged. Neuroimaging demonstrated a structurally normal brain in most affected individuals scanned, although a simplified gyral pattern, abnormal corpus callosum, global reduction in white matter volume, or increased extra-axial spaces and enlarged ventricles have been reported.
LMNB2