Developmental and epileptic encephalopathy 87

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE87 inheritance is autosomal dominant.

Developmental and epileptic encephalopathy 78

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE78 is an autosomal dominant form characterized by onset of refractory seizures in the first days or months of life. Clinical features include severe developmental delay, hypotonia, microcephaly, cortical visual impairment and profound intellectual disability. Some patients manifest a less severe phenotype characterized by pharmacoresponsive epilepsy, autism spectrum disorder and moderate intellectual disability.

Charcot-Marie-Tooth disease, axonal, type 2N

An axonal form of Charcot-Marie-Tooth disease, a disorder of the peripheral nervous system, characterized by progressive weakness and atrophy, initially of the peroneal muscles and later of the distal muscles of the arms. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies (designated CMT1 when they are dominantly inherited) and primary peripheral axonal neuropathies (CMT2). Neuropathies of the CMT2 group are characterized by signs of axonal degeneration in the absence of obvious myelin alterations, normal or slightly reduced nerve conduction velocities, and progressive distal muscle weakness and atrophy.

Developmental and epileptic encephalopathy 46

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent.

Developmental and epileptic encephalopathy 79

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE79 is an autosomal dominant form characterized by onset of refractory seizures in the first months of life. Brain imaging may show hypomyelination, cerebral atrophy and thinning of the corpus callosum.

GLUT1 deficiency syndrome 1

A neurologic disorder showing wide phenotypic variability. The most severe 'classic' phenotype comprises infantile-onset epileptic encephalopathy associated with delayed development, acquired microcephaly, motor incoordination, and spasticity. Onset of seizures, usually characterized by apneic episodes, staring spells, and episodic eye movements, occurs within the first 4 months of life. Other paroxysmal findings include intermittent ataxia, confusion, lethargy, sleep disturbance, and headache. Varying degrees of cognitive impairment can occur, ranging from learning disabilities to severe intellectual disability.

Developmental and epileptic encephalopathy 37

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE37 is an autosomal recessive, severe form manifesting in the first years of life. Affected individuals show hyperkinetic movement disorder with choreoathetosis, spasticity, rigidity, intellectual disability, absent speech, and impaired volitional movements.

Developmental and epileptic encephalopathy 14

A rare epileptic encephalopathy of infancy that combines pharmacoresistant seizures with developmental delay. This severe neurologic disorder is characterized by onset in the first 6 months of life of refractory focal seizures and arrest of psychomotor development. Ictal EEG shows discharges that arise randomly from various areas of both hemispheres and migrate from one brain region to another.

Developmental and epileptic encephalopathy 12

A form of epilepsy characterized by frequent tonic seizures or spasms beginning in infancy with a specific EEG finding of suppression-burst patterns, characterized by high-voltage bursts alternating with almost flat suppression phases. Patients may progress to West syndrome, which is characterized by tonic spasms with clustering, arrest of psychomotor development, and hypsarrhythmia on EEG.

Developmental and epileptic encephalopathy 34

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE34 is characterized by onset of refractory migrating focal seizures in infancy. Affected children show developmental regression and are severely impaired globally.

Polyendocrine-polyneuropathy syndrome

A progressive endocrine and neurodevelopmental disorder manifesting early in childhood with growth retardation and recurrent episodes of profound asymptomatic hypoglycemia. PEPNS is characterized by central hypothyroidism, hypogonadotropic hypogonadism, incomplete puberty, progressive non-autoimmune insulin-dependent diabetes mellitus, peripheral demyelinating sensorimotor polyneuropathy, and cerebellar and pyramidal signs.

Neurodevelopmental disorder with or without hyperkinetic movements and seizures, autosomal dominant

An autosomal dominant neurodevelopmental disorder characterized by severe intellectual disability and developmental delay, absent speech, muscular hypotonia, dyskinesia, and hyperkinetic movements. Cortical blindness, cerebral atrophy, and seizures are present in some patients.

Developmental and epileptic encephalopathy 17

A severe neurologic disorder characterized by onset of intractable seizures in the first weeks or months of life and usually associated with EEG abnormalities. Affected infants have very poor psychomotor development and may have brain abnormalities, such as cerebral atrophy or thin corpus callosum. Some patients may show involuntary movements.

Generalized epilepsy with febrile seizures plus 2

A rare autosomal dominant, familial condition with incomplete penetrance and large intrafamilial variability. Patients display febrile seizures persisting sometimes beyond the age of 6 years and/or a variety of afebrile seizure types. This disease combines febrile seizures, generalized seizures often precipitated by fever at age 6 years or more, and partial seizures, with a variable degree of severity.

Developmental and epileptic encephalopathy 97

A form of epileptic encephalopathy, a heterogeneous group of early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE97 is an autosomal dominant form.

Developmental and epileptic encephalopathy 110

A form of epileptic encephalopathy, a heterogeneous group of early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE110 is an autosomal recessive form characterized by profound global developmental delay and hypotonia apparent in infancy followed by onset of seizures in the first months or years of life.

Developmental and epileptic encephalopathy 66

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE66 is an autosomal dominant form characterized by onset of seizures in first days or weeks of life.

Developmental and epileptic encephalopathy 100

A form of epileptic encephalopathy, a heterogeneous group of early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE100 is an autosomal dominant, severe form characterized by global developmental delay and onset of variable types of seizures in the first months or years of life.

Developmental and epileptic encephalopathy 31A

An autosomal dominant epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent.

Epilepsy, familial adult myoclonic, 4

A form of familial myoclonic epilepsy, a neurologic disorder characterized by cortical hand tremors, myoclonic jerks and occasional generalized or focal seizures with a non-progressive or very slowly progressive disease course. Usually, myoclonic tremor is the presenting symptom, characterized by tremulous finger movements and myoclonic jerks of the limbs increased by action and posture. In a minority of patients, seizures are the presenting symptom. Some patients exhibit mild cognitive impairment. FAME4 inheritance is autosomal dominant.

Focal segmental glomerulosclerosis and neurodevelopmental syndrome

An autosomal dominant disorder characterized by global developmental delay associated with variable features of focal segmental glomerulosclerosis, a renal pathology defined by the presence of segmental sclerosis in glomeruli and resulting in proteinuria, reduced glomerular filtration rate and progressive decline in renal function. Some patients have transient proteinuria and others require renal transplant. Neurodevelopmental features are also variable, with some patients having only mildly impaired intellectual development, and others having a severe developmental disorder associated with early-onset refractory seizures or epileptic encephalopathy. Additional features, including feeding difficulties, poor overall growth, and non-specific dysmorphic facial features, are commonly observed.

Juvenile myoclonic epilepsy 1

A subtype of idiopathic generalized epilepsy. Patients have afebrile seizures only, with onset in adolescence (rather than in childhood) and myoclonic jerks which usually occur after awakening and are triggered by sleep deprivation and fatigue.

Developmental and epileptic encephalopathy 56

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE56 is an autosomal dominant condition.

Developmental and epileptic encephalopathy 18

A severe autosomal recessive neurologic disorder characterized by lack of psychomotor development apparent from birth, dysmorphic facial features, early onset of refractory seizures, and thick corpus callosum and persistent cavum septum pellucidum on brain imaging.

Cutis laxa, autosomal recessive, 2D

A form of cutis laxa, a disorder characterized by an excessive congenital skin wrinkling, a large fontanelle with delayed closure, a typical facial appearance with downslanting palpebral fissures, and a general connective tissue weakness. Most ARCL2D patients exhibit severe hypotonia as well as cardiovascular and neurologic involvement.

Developmental and epileptic encephalopathy 48

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE48 is an autosomal recessive form characterized by onset of seizures in the first year of life. Affected individuals manifest global developmental delay, intellectual disability, absent speech, and poor, if any, motor development.

Epilepsy, familial adult myoclonic, 3

A form of familial myoclonic epilepsy, a neurologic disorder characterized by cortical hand tremors, myoclonic jerks and occasional generalized or focal seizures with a non-progressive or very slowly progressive disease course. Usually, myoclonic tremor is the presenting symptom, characterized by tremulous finger movements and myoclonic jerks of the limbs increased by action and posture. In a minority of patients, seizures are the presenting symptom. Some patients exhibit mild cognitive impairment. FAME3 inheritance is autosomal dominant.

Developmental and epileptic encephalopathy 26

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE26 patients manifest multiple types of seizures, delayed psychomotor development, poor or absent speech, hypotonia, hypsarrhythmia.

Epilepsy, familial adult myoclonic, 1

A form of familial myoclonic epilepsy, a neurologic disorder characterized by cortical hand tremors, myoclonic jerks and occasional generalized or focal seizures with a non-progressive or very slowly progressive disease course. Usually, myoclonic tremor is the presenting symptom, characterized by tremulous finger movements and myoclonic jerks of the limbs increased by action and posture. In a minority of patients, seizures are the presenting symptom. Some patients exhibit mild cognitive impairment. FAME1 inheritance is autosomal dominant.

Epilepsy, familial adult myoclonic, 6

A form of familial myoclonic epilepsy, a neurologic disorder characterized by cortical hand tremors, myoclonic jerks and occasional generalized or focal seizures with a non-progressive or very slowly progressive disease course. Usually, myoclonic tremor is the presenting symptom, characterized by tremulous finger movements and myoclonic jerks of the limbs increased by action and posture. In a minority of patients, seizures are the presenting symptom. Some patients exhibit mild cognitive impairment. FAME6 inheritance is autosomal dominant.

Epilepsy, progressive myoclonic 10

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM10 is an autosomal recessive form characterized by progressive dysarthria, myoclonus, ataxia, cognitive decline, psychosis, dementia and spasticity, with onset in childhood. There is variability between patients.

Intellectual developmental disorder, autosomal dominant 5

A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRD5 patients show global developmental delay with delayed motor development, hypotonia, moderate-to-severe intellectual disability, and severe language impairment. Epilepsy and autism can be present in some patients.

Developmental and epileptic encephalopathy 21

A severe disease characterized by intractable seizures, profound global developmental delay, and persistent severe axial hypotonia as well as appendicular hypertonia.

Cognitive impairment with or without cerebellar ataxia

A disorder characterized by markedly delayed cognitive and motor development, attention deficit disorder, and cerebellar ataxia. Features include bilateral esophoria, strabismatic amblyopia, unsustained gaze evoked nystagmus on horizontal gaze, ataxic gait, dysmetria in the upper limbs and dysarthria, with normal strength, tone, and reflexes.

Seizures, benign familial infantile, 3

A form of benign familial infantile epilepsy, a neurologic disorder characterized by afebrile seizures occurring in clusters during the first year of life, without neurologic sequelae. BFIS3 inheritance is autosomal dominant.

Episodic kinesigenic dyskinesia 1

An autosomal dominant form of paroxysmal kinesigenic dyskinesia, a neurologic condition characterized by recurrent and brief attacks of abnormal involuntary movements, triggered by sudden voluntary movement. These attacks usually have onset during childhood or early adulthood and can involve dystonic postures, chorea, or athetosis.

Seizures, benign familial neonatal 2

A disorder characterized by clusters of seizures occurring in the first days of life. Most patients have spontaneous remission by 12 months of age and show normal psychomotor development. The disorder is distinguished from benign familial infantile seizures by an earlier age at onset.

Seizures, benign familial neonatal 1

A disorder characterized by clusters of seizures occurring in the first days of life. Most patients have spontaneous remission by 12 months of age and show normal psychomotor development. Some rare cases manifest an atypical severe phenotype associated with epileptic encephalopathy and psychomotor retardation. The disorder is distinguished from benign familial infantile seizures by an earlier age at onset. In some patients, neonatal convulsions are followed later in life by myokymia, a benign condition characterized by spontaneous involuntary contractions of skeletal muscles fiber groups that can be observed as vermiform movement of the overlying skin. Electromyography typically shows continuous motor unit activity with spontaneous oligo- and multiplet-discharges of high intraburst frequency (myokymic discharges). Some patients may have isolated myokymia.

Myoclonic-atonic epilepsy

A form of epilepsy characterized by myoclonic-atonic and absence seizures, appearing in early childhood. Patients have delayed development before the onset of seizures and show varying degrees of intellectual disability following seizure onset.

Epilepsy, progressive myoclonic 12

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM12 is an autosomal recessive form characterized by onset of tonic-clonic seizures and/or myoclonus in the second decade of life. Affected individuals develop cerebellar ataxia associated with progressive cerebral and cerebellar atrophy on brain imaging. Most patients lose ambulation and become wheelchair-bound. Additional more variable features include mild cognitive dysfunction or psychiatric manifestations, such as depression or anxiety.

Epilepsy, progressive myoclonic 1

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM1 is an autosomal recessive form characterized by severe, stimulus-sensitive myoclonus and tonic-clonic seizures. The onset, occurring between 6 and 13 years of age, is characterized by convulsions. Myoclonus begins 1 to 5 years later. The twitchings occur predominantly in the proximal muscles of the extremities and are bilaterally symmetrical, although asynchronous. At first small, they become late in the clinical course so violent that the victim is thrown to the floor. Mental deterioration and eventually dementia develop.

Epilepsy, familial focal, with variable foci 1

An autosomal dominant form of epilepsy characterized by focal seizures arising from different cortical regions in different family members. Many patients have an aura and show automatisms during the seizures, whereas others may have nocturnal seizures. There is often secondary generalization. Some patients show abnormal interictal EEG, and some patients may have intellectual disability or autism spectrum disorders. Seizure onset usually occurs in the first or second decades, although later onset has been reported, and there is phenotypic variability within families. Penetrance of the disorder is incomplete.

Epilepsy, childhood absence 5

A subtype of idiopathic generalized epilepsy characterized by an onset at age 6-7 years, frequent absence seizures (several per day) and bilateral, synchronous, symmetric 3-Hz spike waves on EEG. Tonic-clonic seizures often develop in adolescence. Absence seizures may either remit or persist into adulthood.

Spinocerebellar ataxia 6

Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. SCA6 is an autosomal dominant cerebellar ataxia (ADCA), mainly caused by expansion of a CAG repeat in the coding region of CACNA1A. There seems to be a correlation between the repeat number and earlier onset of the disorder.

Developmental and epileptic encephalopathy 39 with leukodystrophy

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE39 is characterized by global hypomyelination of the central nervous system, with the gray matter appearing relatively unaffected. Inheritance is autosomal recessive.

Intellectual developmental disorder, autosomal dominant 6, with or without seizures

A disorder characterized by significantly below average general intellectual functioning associated with impairments in adaptive behavior and manifested during the developmental period. MRD6 additional features may include seizures, hypotonia, abnormal movements, such as dystonia, and autistic features.

Developmental and epileptic encephalopathy 25, with amelogenesis imperfecta

An autosomal recessive disease characterized by subclinical seizures appearing in the first days of life, evolving to severe epileptic disease. Affected individuals have profound or severe delayed development with lack of speech, and most patients do not acquire the ability to sit. Additional variable features include axial hypotonia, peripheral hypertonia, and abnormal involuntary movements such as dystonia and choreoathetosis. Dental abnormalities, including delayed eruption, hypodontia, tooth hypoplasia, yellow discoloration, thin enamel, and enamel chipping are observed in most patients.

Developmental and epileptic encephalopathy 24

A disease characterized by early-onset seizures, intellectual disability of varying degrees, and behavioral disturbances or autistic features in most individuals.

Paroxysmal non-kinesigenic dyskinesia 3 with or without generalized epilepsy

An autosomal dominant neurologic disorder characterized by absence seizures, generalized tonic-clonic seizures, paroxysmal nonkinesigenic dyskinesia and involuntary dystonic or choreiform movements. Onset is usually in childhood. Patients may have seizures only, dyskinesia only, or both.

Epilepsy, progressive myoclonic 11

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM11 is an autosomal dominant form. Clinical features include normal or mildly delayed early development, developmental regression after seizures onset, inability to walk, severely impaired intellectual development, poor or absent speech, spasticity, ataxia, and intention tremor. Brain imaging shows cerebellar atrophy in some patients.

Epilepsy, progressive myoclonic 7

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM7 is an autosomal dominant form characterized by myoclonic epilepsy apparent in the first or second decades of life. Cognitive function may decline in some patients.

Epilepsy, nocturnal frontal lobe, 4

An autosomal dominant focal epilepsy characterized by nocturnal seizures associated with fear sensation, tongue movements, and nocturnal wandering, closely resembling nightmares and sleep walking.

Angelman syndrome

A neurodevelopmental disorder characterized by severe motor and intellectual retardation, ataxia, frequent jerky limb movements and flapping of the arms and hands, hypotonia, seizures, absence of speech, frequent smiling and episodes of paroxysmal laughter, open-mouthed expression revealing the tongue.

Developmental and epileptic encephalopathy 32

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE32 inheritance is autosomal dominant.

Epilepsy, progressive myoclonic 4, with or without renal failure

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM4 is an autosomal recessive form associated with renal failure in some cases. Cognitive function is preserved.

Developmental and epileptic encephalopathy 5

A disorder characterized by seizures associated with hypsarrhythmia, profound intellectual disability with lack of visual attention and speech development, as well as spastic quadriplegia.

Developmental and epileptic encephalopathy 45

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent.

Developmental and epileptic encephalopathy 33

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent.

Lissencephaly, X-linked 2

A classic type lissencephaly associated with abnormal genitalia. Patients have severe congenital or postnatal microcephaly, lissencephaly, agenesis of the corpus callosum, neonatal-onset intractable epilepsy, poor temperature regulation, chronic diarrhea, and ambiguous or underdeveloped genitalia.

Familial infantile myoclonic epilepsy

A subtype of idiopathic epilepsy starting in early infancy and manifesting as myoclonic seizures, febrile convulsions, and tonic-clonic seizures.

Epilepsy, progressive myoclonic 3, with or without intracellular inclusions

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM3 is an autosomal recessive, severe, form with early onset. Multifocal myoclonic seizures begin between 16 and 24 months of age after normal initial development. Neurodegeneration and regression occur with seizure onset. Other features include intellectual disability, dysarthria, truncal ataxia, and loss of fine finger movements. EEG shows slow dysrhythmia, multifocal and occasionally generalized epileptiform discharges. In some patients, ultrastructural findings on skin biopsies identify intracellular accumulation of autofluorescent lipopigment storage material, consistent with neuronal ceroid lipofuscinosis.

Epilepsy, progressive myoclonic 1B

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM1B is an autosomal recessive form characterized by myoclonus that progressed in severity over time, tonic-clonic seizures and ataxia.

Epilepsy, focal, with speech disorder and with or without impaired intellectual development

An autosomal dominant, highly variable neurologic disorder. Features range from severe early-onset seizures associated with delayed psychomotor development, persistent speech difficulties, and intellectual disability to a more benign entity characterized by childhood onset of mild or asymptomatic seizures associated with transient speech difficulties followed by remission of seizures in adolescence and normal psychomotor development. The disorder encompasses several clinical entities, including Landau-Kleffner syndrome, epileptic encephalopathy with continuous spike and wave during slow-wave sleep, autosomal dominant rolandic epilepsy, intellectual disability and speech dyspraxia, and benign epilepsy with centrotemporal spikes.

Developmental and epileptic encephalopathy 74

A form of epileptic encephalopathy, a heterogeneous group of severe early-onset epilepsies characterized by refractory seizures, neurodevelopmental impairment, and poor prognosis. Development is normal prior to seizure onset, after which cognitive and motor delays become apparent. DEE74 is an autosomal dominant form with onset in the first year of life.

Epilepsy, progressive myoclonic 6

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. EPM6 is an autosomal recessive form 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.

Epilepsy, familial focal, with variable foci 4

An autosomal dominant form of epilepsy characterized by focal seizures arising from different cortical regions, including the temporal, frontal, parietal, and occipital lobes. Seizure types commonly include temporal lobe epilepsy, frontal lobe epilepsy, and nocturnal frontal lobe epilepsy. Some patients may have intellectual disability or autism spectrum disorders. Seizure onset usually occurs in the first or second decades, although later onset has been reported, and there is phenotypic variability within families. A subset of patients have structural brain abnormalities. Penetrance of the disorder is incomplete. FFEVF4 is characterized by onset of focal seizures in the first years of life.

Encephalopathy, familial, with neuroserpin inclusion bodies

A neurodegenerative disease clinically characterized by dementia. Additional features include intellectual decline, psychic seizures, progressive myoclonic epilepsy, and cerebral atrophy. Histologically, it is characterized by the presence of eosinophilic inclusion bodies (called Collins bodies) throughout the deeper layers of the cerebral cortex, leading to neuronal death.

Myoclonic epilepsy of Lafora 2

A form of progressive myoclonic epilepsy, a clinically and genetically heterogeneous group of disorders defined by the combination of action and reflex myoclonus, other types of epileptic seizures, and progressive neurodegeneration and neurocognitive impairment. MELF2 is an autosomal recessive, severe form characterized by onset of progressive neurodegeneration between 8 and 18 years of age. Initial features can include headache, myoclonic jerks, generalized seizures, and often visual hallucination. Typically, as seizures increase in frequency, cognitive function declines towards dementia, and affected individuals die usually within 10 years after onset. At the cellular level, MELF2 is characterized by accumulation of starch-like polyglucosans called Lafora bodies (LBs) that are most abundant in organs with the highest glucose metabolism: brain, heart, liver and skeletal muscle.