MedGen

Any generalized epilepsy in which the cause of the disease is a mutation in the CASR gene. [from MONDO]

SCN1A seizure disorders encompass a spectrum that ranges from simple febrile seizures and generalized epilepsy with febrile seizures plus (GEFS+) at the mild end to Dravet syndrome and intractable childhood epilepsy with generalized tonic-clonic seizures (ICE-GTC) at the severe end. Phenotypes with intractable seizures including Dravet syndrome are often associated with cognitive decline. Less commonly observed phenotypes include myoclonic astatic epilepsy (MAE), Lennox-Gastaut syndrome, infantile spasms, epilepsy with focal seizures, and vaccine-related encephalopathy and seizures. The phenotype of SCN1A seizure disorders can vary even within the same family. [from GeneReviews]

GRIN2A-related disorders encompass a broad phenotypic spectrum that includes developmental delay evolving to intellectual disability (DD/ID), epilepsy, speech and language disorders, movement disorders, and neuropsychiatric disorders. Intellect ranges from normal to profoundly impaired. Observed speech disorders include dysarthria and speech dyspraxia, and both receptive and expressive language delays; more mildly affected individuals may display subtly impaired intelligibility of conversational speech. Epilepsy features include seizure onset usually between ages three and six years, focal epilepsy with language and/or global developmental regression, and electroencephalogram (EEG) abnormalities, including continuous spike-and-wave discharges in sleep or very active centrotemporal discharges. Epilepsy is typically focal and ranges from self-limited epilepsy with centrotemporal spikes to developmental and/or epileptic encephalopathies (DEE/EE), including the syndromes of DEE/EE with spike-wave activation in sleep (DEE/EE-SWAS), which include Landau-Kleffner syndrome. Movement disorders occur less frequently and include ataxia, dystonia, and chorea. [from GeneReviews]

FBXL4-related encephalomyopathic mitochondrial DNA (mtDNA) depletion syndrome is a multi-system disorder characterized primarily by congenital or early-onset lactic acidosis and growth failure, feeding difficulty, hypotonia, and developmental delay. Other neurologic manifestations can include seizures, movement disorders, ataxia, autonomic dysfunction, and stroke-like episodes. All affected individuals alive at the time they were reported (median age: 3.5 years) demonstrated significant developmental delay. Other findings can involve the heart (hypertrophic cardiomyopathy, congenital heart malformations, arrhythmias), liver (mildly elevated transaminases), eyes (cataract, strabismus, nystagmus, optic atrophy), hearing (sensorineural hearing loss), and bone marrow (neutropenia, lymphopenia). Survival varies; the median age of reported deaths was two years (range 2 days – 75 months), although surviving individuals as old as 36 years have been reported. To date FBXL4-related mtDNA depletion syndrome has been reported in 50 individuals. [from GeneReviews]

Developmental and epileptic encephalopathy-8 (DEE8) is an X-linked disorder characterized by seizure onset before 2 years of age and severe developmental delay. Some patients have hyperekplexia (summary by Shimojima et al., 2011). For general phenotypic descriptions and discussions of genetic heterogeneity of developmental and epileptic encephalopathy and hyperekplexia, see DEE1 (308350) and HKPX1 (149400), respectively. [from OMIM]

PRRT2-related disorder, caused by heterozygous pathogenic variants in the gene PRRT2 (associated with aberrant synaptic transmission), is characterized by three core episodic neurologic phenotypes: epilepsy, movement disorder, and migraine. Age at onset and phenotypes range from neonatal/infantile (self-limited [familial] infantile epilepsy), to childhood (childhood absence epilepsy), to adolescence to adulthood (paroxysmal kinesigenic dyskinesia [PKD] or migraine). As individuals with PRRT2-related disorder age, they may exhibit one of more of these core phenotypes in various combinations, either concurrently or sequentially. Additionally, family members with the same pathogenic PRRT2 variant may display different core phenotypes. [from GeneReviews]

Osteoporosis-pseudoglioma syndrome (OPPG) is an autosomal recessive disorder characterized by severe osteoporosis and visual disturbance from childhood. Juvenile onset of osteoporosis manifests as long-bone fractures, vertebral compression fractures, kyphoscoliosis, deformity of extremities, and short stature. Congenital or early-onset visual disturbances arise from ophthalmologic problems including retinal detachment and microphthalmia (summary by Narumi et al., 2010). [from OMIM]

Autosomal dominant epilepsy with auditory features (ADEAF) is a focal epilepsy syndrome with auditory symptoms and/or receptive aphasia as prominent ictal manifestations. The most common auditory symptoms are simple unformed sounds including humming, buzzing, or ringing; less common forms are distortions (e.g., volume changes) or complex sounds (e.g., specific songs or voices). Ictal receptive aphasia consists of a sudden onset of inability to understand language in the absence of general confusion. Less commonly, other ictal symptoms may occur, including sensory symptoms (visual, olfactory, vertiginous, or cephalic) or motor, psychic, and autonomic symptoms. Age at onset is usually in adolescence or early adulthood (age 10-30 years). The clinical course of ADEAF is benign. Seizures are usually well controlled after initiation of medical therapy. [from GeneReviews]

Focal cortical dysplasia type II (FCORD2), or focal cortical dysplasia of Taylor (FCDT), is a cerebral developmental malformation that results in a clinical phenotype of intractable epilepsy, usually requiring surgery. FCORD2 has been classified histologically into 2 subtypes: a type without balloon cells, known as type IIA, and a type with balloon cells, known as type IIB (Palmini et al., 2004). Affected individuals have refractory seizures, usually with onset in early childhood, and may have persistent intellectual disability. Most patients require neurosurgical resection of affected brain tissue to ameliorate seizure frequency and severity (summary by Moller et al., 2016). [from OMIM]

The neuronal ceroid lipofuscinoses (NCL; CLN) are a clinically and genetically heterogeneous group of neurodegenerative disorders characterized by the intracellular accumulation of autofluorescent lipopigment storage material in different patterns ultrastructurally. The lipopigment patterns observed most often in CLN8 comprise mixed combinations of 'granular,' 'curvilinear,' and 'fingerprint' profiles (Mole et al., 2005). For a general phenotypic description and a discussion of genetic heterogeneity of CLN, see CLN1 (256730). [from OMIM]

Pitt-Hopkins-like syndrome-1 (PTHSL1) is an autosomal recessive neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability, severe speech impairment or regression, and behavioral abnormalities. Most patients have onset of seizures within the first years of life. Some patients may have cortical dysplasia on brain imaging (summary by Smogavec et al., 2016). [from OMIM]

Benign familial neonatal-infantile seizures is an autosomal dominant disorder in which afebrile seizures occur in clusters during the first year of life, without neurologic sequelae (Shevell et al., 1986). For a general phenotypic description and a discussion of genetic heterogeneity of benign familial infantile seizures, see BFIS1 (601764). [from OMIM]

Pelizaeus-Merzbacher-like disease 1 (PMLD1) is a slowly progressive leukodystrophy that typically presents during the neonatal or early-infantile period with nystagmus, commonly associated with hypotonia, delayed acquisition of motor milestones, speech delay, and dysarthria. Over time the hypotonia typically evolves into spasticity that affects the ability to walk and communicate. Cerebellar signs (gait ataxia, dysmetria, intention tremor, head titubation, and dysdiadochokinesia) frequently manifest during childhood. Some individuals develop extrapyramidal movement abnormalities (choreoathetosis and dystonia). Hearing loss and optic atrophy are observed in rare cases. Motor impairments can lead to swallowing difficulty and orthopedic complications, including hip dislocation and scoliosis. Most individuals have normal cognitive skills or mild intellectual disability – which, however, can be difficult to evaluate in the context of profound motor impairment. [from GeneReviews]

GRIN2B-related neurodevelopmental disorder is characterized by mild to profound developmental delay / intellectual disability (DD/ID) in all affected individuals. Muscle tone abnormalities (spasticity and/or hypotonia, occasionally associated with feeding difficulties), as well as epilepsy and autism spectrum disorder (ASD) / behavioral issues, are common. Other infantile- or childhood-onset findings include microcephaly; dystonic, dyskinetic, or choreiform movement disorder; and/or cortical visual impairment. Brain MRI reveals a malformation of cortical development in a minority of affected individuals. To date, fewer than 100 individuals with GRIN2B-related neurodevelopmental disorder have been reported. [from GeneReviews]

SCN8A-related epilepsy and/or neurodevelopmental disorders encompasses a spectrum of phenotypes. Epilepsy phenotypes include developmental and epileptic encephalopathy (DEE) associated with severe developmental delays and usually pharmacoresistant epilepsy with multiple seizure types; mild-to-moderate developmental and epileptic encephalopathy (mild/modDEE, or intermediate epilepsy) with partially treatable epilepsy; self-limited familial infantile epilepsy (SeLFIE, also known as benign familial infantile epilepsy or BFIE) with normal cognition and medically treatable seizures; neurodevelopmental delays with generalized epilepsy (NDDwGE); and neurodevelopmental disorder without epilepsy (NDDwoE) with mild-to-moderate intellectual disability (though it can be severe in ~10% of affected individuals). Hypotonia and movement disorders including dystonia, ataxia, and choreoathetosis are common in some phenotypes. Sudden unexpected death in epilepsy (SUDEP) has been reported in some affected individuals. [from GeneReviews]

Spinocerebellar ataxia-29 (SCA29) is an autosomal dominant neurologic disorder characterized by onset in infancy of delayed motor development and mild cognitive delay. Affected individuals develop a very slowly progressive or nonprogressive gait and limb ataxia associated with cerebellar atrophy on brain imaging. Additional variable features include nystagmus, dysarthria, and tremor (summary by Huang et al., 2012). For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400). [from OMIM]

Primary coenzyme Q10 deficiency-7 (COQ10D7) is an autosomal recessive disorder resulting from mitochondrial dysfunction. Most patients have onset of severe cardiac or neurologic symptoms soon after birth, usually resulting in death. Rare patients may have later onset with a more protracted course. Tissue samples from affected individuals show decreased levels of coenzyme Q10 (CoQ10) (summary by Brea-Calvo et al., 2015). For a general phenotypic description and a discussion of genetic heterogeneity of primary coenzyme Q10 deficiency, see COQ10D1 (607426). [from OMIM]

Progressive myoclonus epilepsy, Lafora type (also known as Lafora disease) is characterized by focal occipital seizures presenting as transient blindness or visual hallucinations and fragmentary, symmetric, or generalized myoclonus occurring in previously healthy individuals. Typical age of onset is eight to 19 years (peak: age14-16 years). Generalized tonic-clonic seizures, atypical absence seizures, atonic seizures, and focal seizures with impaired awareness may also occur. The course of the disease is characterized by increasing frequency and intractability of seizures. Status epilepticus with any of the seizure types is common. Cognitive decline becomes apparent at or soon after the onset of seizures. Dysarthria and ataxia appear early, while spasticity appears late. Emotional disturbances and confusion are common in the early stages of the disease and are followed by dementia. Most affected individuals die within ten years of onset, usually from status epilepticus or from complications related to neurologic degeneration. [from GeneReviews]

GRIN1-related neurodevelopmental disorder (GRIN1-NDD) is characterized by mild-to-profound developmental delay / intellectual disability (DD/ID) in all affected individuals. Other common manifestations are epilepsy, muscular hypotonia, movement disorders, spasticity, feeding difficulties, and behavior issues. A subset of individuals show a malformation of cortical development consisting of extensive and diffuse bilateral polymicrogyria. To date, 72 individuals with GRIN1-NDD have been reported. [from GeneReviews]

CLCN4-related neurodevelopmental disorder (CLCN4-NDD), an X-linked disorder, is characterized in the 36 males reported to date by developmental delay or intellectual disability, behavioral/mental health issues (e.g., autism spectrum disorder, anxiety, hyperactivity, and bipolar disorder), epilepsy, and gastrointestinal dysfunction. The five heterozygous females with a de novo CLCN4 variant reported to date had findings very similar to those of affected males. Twenty-two of 25 heterozygous females identified in family studies following identification of an affected male were unaffected or had only mild specific learning difficulties and/or mental health concerns, whereas three were more severely affected. [from GeneReviews]