Familial adult myoclonic epilepsy-1 (FAME1), also known as familial cortical myoclonic tremor associated with epilepsy-1 (FCMTE1), is characterized by autosomal dominant, adult-onset cortical myoclonus, with seizures in 40% of patients. Myoclonus is usually the first symptom and is characterized by tremulous finger movements and myoclonus of the extremities (summary by Depienne et al., 2010). FAME1 tends to occur in patients of southern Asian descent (summary by Bennett et al., 2020). Genetic Heterogeneity of Familial Adult Myoclonic Epilepsy See also FAME2 (607876), caused by mutation in the STARD7 gene (616712) on chromosome 2q11; FAME3 (613608), caused by mutation in the MARCHF6 gene (613297) on chromosome 5p15; FAME4 (615127), which maps to chromosome 3q26.32-q28; FAME6 (618074), caused by mutation in the TNRC6A gene (610739) on chromosome 16p12; and FAME7 (618075), caused by mutation in the RAPGEF2 gene (609530) on chromosome 4. The disorder previously designated FAME5 has been reclassified as a type of autosomal recessive early-onset epilepsy (EPEO5; 615400). Progressive myoclonic epilepsy is a more severe disorder (see, e.g., EPM1, 254800).

Familial adult myoclonic epilepsy-2 (FAME2) is an autosomal dominant neurologic disorder characterized by onset of tremor affecting the fingers, hand, and voice in adolescence or young adulthood with somewhat later onset of rhythmic myoclonic jerks and generalized tonic-clonic seizures. Electrophysiologic studies are consistent with cortical reflex myoclonus. Some patients may show cognitive decline or migraines; photosensitivity is common (summary by De Fusco et al., 2014; Crompton et al., 2012). For a phenotypic description and a discussion of genetic heterogeneity of familial adult myoclonic epilepsy, see FAME1 (601068).

The photoparoxysmal response (PPR), also referred to as photosensitivity, is defined as the abnormal occurrence of cortical spikes or spike and wave discharges on electroencephalogram (EEG) in response to intermittent light stimulation (Doose and Waltz, 1993). Photosensitivity is a frequent finding in patients with idiopathic generalized epilepsy (see 600669), especially those with juvenile myoclonic epilepsy, suggesting a common epileptogenic pathway for both phenomena. The comorbidity of the 2 disorders suggests that presence of PPR may also increase the risk for epilepsy (Stephani et al., 2004; Tauer et al., 2005). Genetic Heterogeneity of Photoparoxysmal Response The PPR1 locus has been mapped to chromosome 6p21. See also PPR2 (609572), mapped to chromosome 13q31, and PPR3 (609573), mapped to chromosome 7q32.

Familial adult myoclonic epilepsy-3 (FAME3) is an autosomal dominant neurologic disorder characterized by onset of cortical tremor, mainly affecting the hands and voice, between 10 and 40 years of age, with adult onset being more common. Most affected individuals develop epilepsy with generalized tonic-clonic seizures; some may have partial or absence seizures. The disorder is nonprogressive or slowly progressive, and most patients respond to antiseizure medication (summary by Florian et al., 2019). For a phenotypic description and a discussion of genetic heterogeneity of familial adult myoclonic epilepsy, see FAME1 (601068).

Developmental and epileptic encephalopathy-19 (DEE19) is a neurologic disorder characterized by the onset of various types of seizures in the first year of life, usually between 8 and 12 months of age. Seizures are often triggered by fever, and status epilepticus may occur. Affected individuals subsequently show mildly to moderately impaired intellectual development. Brain imaging is typically normal. The clinical phenotype is similar to that of Dravet syndrome (DRVT; 607208) (summary by Carvill et al., 2014). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

Progressive myoclonic epilepsy-8 (EPM8) is a rare autosomal recessive form of progressive myoclonic epilepsy with phenotypic variability including ataxia and other movement disorders in addition to myoclonus (summary by Godeiro et al., 2018). For a discussion of genetic heterogeneity of progressive myoclonic epilepsy, see EPM1A (254800).

Developmental and epileptic encephalopathy-100 (DEE100) is a severe neurologic disorder characterized by global developmental delay and onset of variable types of seizures in the first months or years of life. Most patients have refractory seizures and show developmental regression after seizure onset. Affected individuals have ataxic gait or inability to walk and severe to profoundly impaired intellectual development, often with absent speech. Additional more variable features may include axial hypotonia, hyperkinetic movements, dysmorphic facial features, and brain imaging abnormalities (summary by Schneider et al., 2021). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.

Neurodevelopmental disorder with dystonia and seizures (NEDDS) is a severe autosomal recessive disorder characterized by hypotonia and dystonic posturing apparent from early infancy. Affected individuals show global developmental delay with inability to walk or speak and have profoundly impaired intellectual development, often with behavioral abnormalities. Additional features may include other extrapyramidal movements, seizures or seizure-like activity, and cerebellar hypoplasia on brain imaging (Sleiman et al., 2022).