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Seizures, benign familial neonatal, 2(BFNC2; BFNS2)

MedGen UID:
377707
Concept ID:
C1852581
Disease or Syndrome
Synonyms: Benign Neonatal Epilepsy 2; CONVULSIONS, BENIGN FAMILIAL NEONATAL, 2; KCNQ3-Related Benign Familial Neonatal Epilepsy; KCNQ3-related disorders; Seizures, benign neonatal, 2
 
Gene (location): KCNQ3 (8q24.22)
 
Monarch Initiative: MONDO:0007366
OMIM®: 121201

Disease characteristics

Excerpted from the GeneReview: KCNQ3-Related Disorders
KCNQ3-related disorders include self-limited familial neonatal epilepsy (SLFNE) and self-limited familial infantile epilepsy (SLFIE), seizure disorders that occur in children who typically have normal psychomotor development. An additional KCNQ3-related neurodevelopmental disorder (NDD) with and without epilepsy has also been described. In KCNQ3-SLFNE, seizures begin in an otherwise healthy infant between age days two and eight of life and spontaneously disappear within the first year of life. Seizures are generally brief, lasting one to two minutes. Seizure types include tonic or apneic episodes and focal clonic activity, with or without autonomic changes. Motor activity may be confined to one body part, migrate to other regions, or generalize. Infants are normal between seizures and feed normally. In KCNQ3-SLFIE, seizures start in the first year of life beyond the neonatal period and disappear after age one to two years. Seizures are generally brief, lasting two minutes; they appear as daily repeated clusters. Seizure types are usually focal, but can also include generalized, causing diffuse hypertonia with jerks of the limbs, head deviation, or motor arrest with unconsciousness and cyanosis. Infants are normal between seizures and psychomotor development is usually normal. In KCNQ3-NDD, individuals present with intellectual disability with or without seizures and/or cortical visual impairment. As little clinical information on these individuals is available, the clinical presentation of KCNQ3-NDD remains to be defined. [from GeneReviews]
Authors:
Francesco Miceli  |  Maria Virginia Soldovieri  |  Sarah Weckhuysen, et. al.   view full author information

Additional descriptions

From OMIM
Benign familial neonatal seizures-2 is an autosomal dominant neurologic condition characterized by onset of clonic or tonic-clonic seizures in the first few days of life. Seizures tend to last for about a minute, may occur several times a day, and are responsive to medication. Almost all patients have full remission within the first months of life, although some rare patients may have a few seizures later in childhood. EEG, brain imaging, and psychomotor development are usually normal (summary by Fister et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of benign familial neonatal seizures, see BFNS1 (121200).  http://www.omim.org/entry/121201
From MedlinePlus Genetics
Benign familial neonatal seizures (BFNS) is a condition characterized by recurrent seizures in newborn babies. The seizures begin around day 3 of life and usually go away within 1 to 4 months. The seizures can involve only one side of the brain (focal seizures) or both sides (generalized seizures). This condition is often associated with generalized tonic-clonic seizures (also known as grand mal seizures). This type of seizure involves both sides of the brain and affects the entire body, causing a combination of seizure types: tonic seizures, which are characterized by uncontrolled muscle stiffness and rigidity, and clonic seizures, which are characterized by uncontrolled jerking of the muscles. Seizure episodes in infants with BFNS typically begin with tonic stiffness and pauses in breathing (apnea) followed by clonic jerking. 

A test called an electroencephalogram (EEG) is used to measure the electrical activity of the brain. Abnormalities on an EEG test, measured during no seizure activity, can indicate a risk for seizures. However, infants with BFNS usually have normal EEG readings. In some affected individuals, the EEG shows a specific abnormality called the theta pointu alternant pattern. By age 2, most affected individuals who had EEG abnormalities have a normal EEG reading.

Typically, seizures are the only symptom of BFNS, and most people with this condition develop normally. However, some affected individuals develop intellectual disability that becomes noticeable in early childhood. A small percentage of people with BFNS also have a condition called myokymia, which is an involuntary rippling movement of the muscles. In addition, in about 15 percent of people with BFNS, recurrent seizures (epilepsy) will come back later in life after the seizures associated with BFNS have gone away. The age that epilepsy begins is variable.  https://medlineplus.gov/genetics/condition/benign-familial-neonatal-seizures

Clinical features

From HPO
Bilateral tonic-clonic seizure
MedGen UID:
141670
Concept ID:
C0494475
Sign or Symptom
A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Focal clonic seizure
MedGen UID:
155749
Concept ID:
C0752323
Disease or Syndrome
A focal clonic seizure is a type of focal motor seizure characterized by sustained rhythmic jerking, that is regularly repetitive.
Intellectual disability
MedGen UID:
811461
Concept ID:
C3714756
Mental or Behavioral Dysfunction
Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

Recent clinical studies

Diagnosis

Benetou C, Papailiou S, Maritsi D, Anagnostopoulou K, Kontos H, Vartzelis G
Turk J Pediatr 2019;61(2):279-281. doi: 10.24953/turkjped.2019.02.020. PMID: 31951342
Lee IC, Yang JJ, Li SY
J Formos Med Assoc 2017 Sep;116(9):711-719. Epub 2016 Dec 27 doi: 10.1016/j.jfma.2016.11.009. PMID: 28038823

Prognosis

Lee IC, Yang JJ, Li SY
J Formos Med Assoc 2017 Sep;116(9):711-719. Epub 2016 Dec 27 doi: 10.1016/j.jfma.2016.11.009. PMID: 28038823
Miceli F, Soldovieri MV, Ambrosino P, De Maria M, Migliore M, Migliore R, Taglialatela M
J Neurosci 2015 Mar 4;35(9):3782-93. doi: 10.1523/JNEUROSCI.4423-14.2015. PMID: 25740509Free PMC Article

Clinical prediction guides

Lee IC, Yang JJ, Li SY
J Formos Med Assoc 2017 Sep;116(9):711-719. Epub 2016 Dec 27 doi: 10.1016/j.jfma.2016.11.009. PMID: 28038823
Orhan G, Bock M, Schepers D, Ilina EI, Reichel SN, Löffler H, Jezutkovic N, Weckhuysen S, Mandelstam S, Suls A, Danker T, Guenther E, Scheffer IE, De Jonghe P, Lerche H, Maljevic S
Ann Neurol 2014 Mar;75(3):382-94. Epub 2014 Mar 18 doi: 10.1002/ana.24080. PMID: 24318194

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