No abstract

Myoclonic epilepsies with onset in infancy and childhood are clinically and etiologically heterogeneous. Although genetic factors are thought to play an important role, to date very little is known about the etiology of these disorders. We ascertained a large Italian pedigree segregating a recessive idiopathic myoclonic epilepsy that starts in early infancy as myoclonic seizures, febrile convulsions, and tonic-clonic seizures. We typed 304 microsatellite markers spanning the 22 autosomes and mapped the locus on chromosome 16p13 by linkage analysis. A maximum LOD score of 4.48 was obtained for marker D16S3027 at recombination fraction 0. Haplotype analysis placed the critical region within a 3.4-cM interval between D16S3024 and D16S423. The present report constitutes the first example of an idiopathic epilepsy that is inherited as an autosomal recessive trait.

Summary:Purpose: To describe the clinical features of a large kindred with familial infantile myoclonic epilepsy (FIME) with autosomal recessive inheritance, and to discuss the nosology of the early infantile myoclonic epilepsies (IMEs).Methods: The family descends from the intermarriage of two couples of siblings. In a previous study, we mapped the genetic locus to chromosome 16p13.We analyzed results of family records and personal history, psychomotor development, neurologic examination, epilepsy features, and EEG recordings for each subject.Results: FIME has a strong penetrance (eight affected of 14 subjects) and a homogeneous clinical picture. Like the benign form of infantile myoclonic epilepsy (BIME), FIME is a true idiopathic IME with unremarkable history, no neurologic or mental impairment, good response to treatment, and normal interictal EEG pattern. Conversely, onset with generalized epileptic seizures without fever (four patients) or with fever (one patient), frequency and duration of the myoclonic seizures, occurrence of generalized tonic-clonic seizures (GTCSs) in all patients and persistence of seizures into adulthood are characteristics of the severe infantile myoclonic epilepsy (SIME).Conclusions: Clinical overlap probably exists among the myoclonic epilepsies of infancy. FIME differs from other forms of IME in its phenotypic features. The peculiar mode of inheritance is explained by the genetic background of the family. Genetic studies suggest linkage to chromosome 16 in familial cases of true IME.

A father and three of his offspring had skeletal abnormalities consisting of a short forearm, cubitus valgus, fusion of first and second cervical vertebrae, and cleft of L5 and S1. All four had a reciprocal, apparently balanced, translocation 2;8(q32;p13). Normal sibs had normal chromosomes. We conclude that this may be a rare instance of an autosomal dominant condition associated with a balanced chromosome translocation.

Intractable epilepsy and peculiar EEG patterns characterize ring chromosome 20 syndrome [r(20)], while dysmorphic features, mental retardation and behavioural disturbances are widely variable. The clinical evolution of r(20) over time is not well defined as relatively few cases have been reported. Here we describe a patient with severe clinical features followed for a 25-year period. The patient was subjected to clinical, psychometric and EEG evaluation twice a year from the age of 21 years. Cytogenetic studies, using chromosome analysis and fluorescence in situ hybridization (FISH) and several immunological investigations were performed. Ring chromosome 20 was found in 50% of examined metaphases with the deletion of subtelomeric regions 20p and 20q. Our patient presented with marked dysmorphic features, severe mental retardation, tetraparesis, dysarthria and intractable epilepsy with onset during the first year of life. During follow up, EEG findings and clinical features progressively worsened: a progressive disorganization of background EEG activity occurred and mental and motor impairment evolved. The severity of clinical expression depended on the extent of chromosomal deletion and on the haploinsufficiency of other important related genetic loci due to ring instability. The progressive worsening of both clinical and EEG features over a long period, which has also been reported by other authors, further characterized this syndrome.