MedGen

PRRT2-associated paroxysmal movement disorders (PRRT2-PxMD) include paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy (BFIE), paroxysmal kinesigenic dyskinesia with infantile convulsions (PKD/IC), and hemiplegic migraine (HM). In addition, PRRT2 pathogenic variants have been identified in other childhood-onset movement disorders and different types of seizures, suggesting that the understanding of the spectrum of PRRT2-PxMD is still evolving. The paroxysmal attacks in PKD are characterized by dystonia, choreoathetosis, and less commonly ballismus. The seizures of BFIE are usually focal with or without generalization. Thirty percent of PRRT2-associated PKD is associated with BFIE and is referred to as PKD/IC. [from GeneReviews]

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]

Benign familial infantile seizures (BFIS) is a seizure disorder of early childhood with age at onset from 3 months up to 24 months. It is characterized by brief seizures beginning with slow deviation of the head and eyes to 1 side and progressing to generalized motor arrest and hypotonia, apnea and cyanosis, and limb jerks. Seizures usually occur in clusters over a day or several days. The ictal EEG shows focal parietal-temporal activity, whereas the interictal EEG is normal. Concurrent and subsequent psychomotor and neurologic development are normal (Franzoni et al., 2005). See also benign familial neonatal seizures (BFNS1; 121200). Deprez et al. (2009) provided a review of the genetics of epilepsy syndromes starting in the first year of life, and included a diagnostic algorithm. Genetic Heterogeneity of Benign Familial Infantile Seizures The BFIS1 locus has been mapped to chromosome 19q. BFIS2 (605751) is caused by mutation in the PRRT2 gene on chromosome 16p11. BFIS3 (607745), which is caused by the mutations in the SCN2A gene (182390) on chromosome 2q24, has a slightly earlier age at onset and is sometimes termed benign familial 'neonatal-infantile' seizures. BFIS4 (612627) has been mapped to chromosome 1p. BFIS5 (617080) is caused by mutation in the SCN8A gene (600702) on chromosome 12q13. BFIS6 (see 610353) is caused by mutation in the CHRNA2 gene (118502) on chromosome 8p21. [from OMIM]

Lack of observable abnormal electroencephalographic (EEG) patterns in an individual with a history of seizures. About half of individuals with epilepsy show interictal epileptiform discharges upon the first investigation. The yield can be increased by repeated studies, sleep studies, or by ambulatory EEG recordings over 24 hours. Normal interictal EEG is a sign that can be useful in the differential diagnosis. [from HPO]