Rett syndrome. A commonly overlooked progressive encephalopathy in girls

Epigenetic control of adaptive or homeostatic splicing during interval-training activities

Interval-training activities induce adaptive cellular changes without altering their fundamental identity, but the precise underlying molecular mechanisms are not fully understood. In this study, we demonstrate that interval-training depolarization (ITD) of pituitary cells triggers distinct adaptive or homeostatic splicing responses of alternative exons. This occurs while preserving the steady-state expression of the Prolactin and other hormone genes. The nature of these splicing responses depends on the exon's DNA methylation status, the methyl-C-binding protein MeCP2 and its associated CA-rich motif-binding hnRNP L. Interestingly, the steady expression of the Prolactin gene is also reliant on MeCP2, whose disruption leads to exacerbated multi-exon aberrant splicing and overexpression of the hormone gene transcripts upon ITD, similar to the observed hyperprolactinemia or activity-dependent aberrant splicing in Rett Syndrome. Therefore, epigenetic control is crucial for both adaptive and homeostatic splicing and particularly the steady expression of the Prolactin hormone gene during ITD. Disruption in this regulation may have significant implications for the development of progressive diseases.

DIA1R is an X-linked gene related to Deleted In Autism-1

Background

Autism spectrum disorders (ASDs) are frequently occurring disorders diagnosed by deficits in three core functional areas: social skills, communication, and behaviours and/or interests. Mental retardation frequently accompanies the most severe forms of ASDs, while overall ASDs are more commonly diagnosed in males. Most ASDs have a genetic origin and one gene recently implicated in the etiology of autism is the Deleted-In-Autism-1 (DIA1) gene.

Methodology/Principal Findings

Using a bioinformatics-based approach, we have identified a human gene closely related to DIA1, we term DIA1R (DIA1-Related). While DIA1 is autosomal (chromosome 3, position 3q24), DIA1R localizes to the X chromosome at position Xp11.3 and is known to escape X-inactivation. The gene products are of similar size, with DIA1 encoding 430, and DIA1R 433, residues. At the amino acid level, DIA1 and DIA1R are 62% similar overall (28% identical), and both encode signal peptides for targeting to the secretory pathway. Both genes are ubiquitously expressed, including in fetal and adult brain tissue.

Conclusions/Significance

Examination of published literature revealed point mutations in DIA1R are associated with X-linked mental retardation (XLMR) and DIA1R deletion is associated with syndromes with ASD-like traits and/or XLMR. Together, these results support a model where the DIA1 and DIA1R gene products regulate molecular traffic through the cellular secretory pathway or affect the function of secreted factors, and functional deficits cause disorders with ASD-like symptoms and/or mental retardation.

Rett syndrome: a case presenting with atypical seizures. Neurophysiological and clinical aspects

OBJECTIVE

To describe a specific electroclinical type of epileptic seizure in a patient with Rett syndrome.

PATIENT AND METHODS

We present the case of a girl with Rett syndrome and epilepsy, whose seizures followed two differentiated phases, namely (a) a brief hypertonic onset with tonic-axial predominance, followed by (b) a posterior prolonged clinical absence. These two phases were associated, respectively, to a paroxystic desynchronisation or generalised rapid spikes discharges, followed by a critical slow activity.

CONCLUSIONS

The epileptic seizures described in this report have not been previously documented in Rett syndrome. We review and discuss pathophysiological hypotheses in the light of this and previously reported cases of the syndrome.

Infantile hypotonia as a presentation of Rett syndrome

Rett syndrome (RTT) is classically defined by meeting certain clinical diagnostic criteria. It affects mostly females, and one possible pathogenic mechanism was considered to involve mitochondrial function. This was based on the finding of ultrastructural alterations in the mitochondria and decreased respiratory chain enzyme activity. However, the principal etiology of RTT has since been found to be mutations in the MECP2 gene, which is located on the X chromosome. Molecular analysis has allowed the phenotype of MECP2 mutations to be broadened beyond RTT to include girls who have mild mental retardation, autism, and an Angelman syndrome phenotype, as well as males with severe encephalopathy. We present a girl with a previously described mutation in the MECP2 gene whose phenotype is of atypical RTT. She presented with hypotonia and developmental delay in infancy without a clear period of normal development. As part of her evaluation for hypotonia, a muscle biopsy and respiratory chain enzyme analysis showed a slight decrease in respiratory chain enzyme activity consistent with previous reports. This report supports broadening the phenotype of patients who should be considered for MECP2 mutation analysis to include cases of developmental delay and hypotonia without evidence of an initial period of normal development. Furthermore, it supports the hypothesis of an underlying secondary defect in energy metabolism contributing to the pathogenesis of RTT.

Rett syndrome: methyl-CpG-binding protein 2 mutations and phenotype-genotype correlations

Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder that manifests in females, typically after the first year of life. It is a leading cause of mental retardation and autistic behavior in girls and women; a hallmark of the disease is incessant hand movements in the form of wringing, twisting, or clapping. It was recently discovered that RTT is caused by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. MECP2 assists in the transcriptional silencing process via DNA methylation; we hypothesize that disruption of this gene alters the normal developmental expression of various other genes, some of which must account for the peculiar neurologic phenotype of RTT. Molecular studies have identified MECP2 mutations in up to 80% of classic RTT patients; mutation type has some effect on the phenotypic manifestation of RTT, but the pattern of X inactivation seems to determine phenotypic severity. Favorable (skewed) X inactivation can so spare a patient from the effects of mutant MECP2 that they display only the mildest learning disability or no phenotype at all. The unmitigated impact of mutant MECP2 can be inferred from the few males who have been born into RTT kindreds with such severe neonatal encephalopathy that they did not survive their second year. MECP2 mutations thus manifest in a far broader array of phenotypes than classic RTT. This discovery should prove helpful in diagnosing cases of mild learning disability or severe neonatal encephalopathies of unknown cause and also should provide insight into the pathogenesis of RTT.

Síndrome de Rett: estudo retrospectivo e prospectivo de 28 pacientes

No período entre Novembro 1982 e Maio 1999, 28 crianças com Síndrome de Rett foram seguidas por um período médio de 6 anos e 2 meses.O início da regressão do desenvolvimento psicomotor ocorreu entre 5 e 20 meses.Os 19 casos de síndrome de Rett típica apresentavam períodos pré e perinatal normais,e evoluíram com perda das habilidades previamente adquiridas, retardo psicomotor e estereotipias de mãos; 16 tinham desaceleração do crescimento craniano e 12 tinham marcha anormal. Nove pacientes foram casos atípicos: 2 formas frustras, 2 congênitas, 3 com crises precoces, 1 com fala preservada e 1 sendo do sexo masculino. A epilepsia esteve presente em 21 pacientes com crises predominantemente parciais e a droga de escolha foi a carbamazepina (15 pacientes). Na avaliação inicial a maioria dos pacientes estava distribuída em estágios II e III da síndrome e evolutivamente passaram aos estágios III e IV, sendo que 3 faleceram.

Rett syndrome

Rett syndrome is a progressive neurodegenerative disease of unknown etiology. Reported here are three children who presented with all clinical features of Rett syndrome. The aim of this presentation is to alert physicians to the existence of this progressive brain disease which only affects girls and so far no specific treatment has been suggested.

Using genetic epidemiology to study Rett syndrome: the design of a case-control study

Rett syndrome is a neurological disorder that is seen almost exclusively in females. Although generally considered to have a genetic basis, the underlying mechanism remains obscure. One favoured hypothesis is that the syndrome is an X-linked dominant disorder, lethal or non-expressed in males. Genealogical research has also suggested that the mode of transmission in Rett syndrome may involve a premutation which over several generations is converted to a full mutation. Geographical clustering has been reported, and it has also been proposed that Rett syndrome is a clinically variable condition and that other neurological disorders may be occurring more commonly in families with Rett syndrome. Other studies have found an apparent increase in intellectual disability and seizures in the extended families of girls with Rett syndrome. The science of genetic epidemiology can be used to identify familial aggregation, which is the clustering of a disorder within a family. We have used a case-control study design to investigate both fetal wastage and familial aggregation of other disorders in families of girls with Rett syndrome. The Australian Rett Syndrome Database provided the source of cases, and control probands were girls of a similar age with normal development. This paper describes the methodology for a case-control study of this rare condition using pedigree data and discusses issues in the collection and evaluation of such data. The use of a control population is an important feature. Both the strengths and the shortcomings of our design are identified, and recommendations are made for future research.

Japanese monozygotic twins with Rett syndrome

We present a study of 28-year-old Japanese monozygotic female twins with Rett syndrome (RS). To our knowledge, this is the first report of monozygotic twins with RS from Japanese family. There are some differences between twins about seizures, scoliosis and stereotypical hand movements during adolescence. Monozygosity was confirmed by both blood typing and HLA titers.

Rett syndrome: an analysis using Sartwell's incubation period model

Evidence suggests that Rett syndrome is a genetic disorder; however, an etiologic genetic model has yet to be identified. The purpose of this study was to apply a statistical model, Sartwell's incubation period model, to estimate the incubation period of Rett syndrome and postulate further on the etiology of Rett syndrome. Sartwell's model was used to test the hypothesis that the age of onset of developmental regression distributions approximate a logarithmic normal model and thus the etiologic factors of Rett syndrome occur in utero or prior to conception. Data from three case-series of Rett syndrome from different geographic regions were used for the analyses. Curves resulting from the analyses demonstrated a good approximation to the logarithmic normal distribution, indicating a good fit of the data to Sartwell's model. In conclusion, the incubation period of Rett syndrome fits the logarithmic normal model, which is consistent with the theory that a major causal factor for Rett syndrome most likely occurs in utero or prior to conception, eg, a defective gene.

Rett syndrome

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Mitochondrial dysfunction in Rett syndrome. An ultrastructural and biochemical study

We report the ultrastructural and biochemical alterations of muscle mitochondria in two girls with Rett syndrome. Our findings suggest the presence of an energy metabolism impairment the primary or secondary role of which in the pathogenesis of this syndrome cannot be defined at present.

Staring episodes in children analyzed by telemetry

Staring episodes in children may be ictal or nonictal, and telemetry helps make this distinction. Twenty-seven children referred to our service for elucidating the nature of their staring spells were studied by telemetry. No staring events were recorded in four children. The staring events were not associated with electroencephalographic (EEG) changes in 12 children. In 11 children, the staring events had EEG accompaniments: four had generalized spike-and-wave changes; three had focal or asymmetrical changes; and four had generalized decrement (desynchronization), which has not been described before as an electrical correlate of staring. EEG video telemetry in this group of patients led to accurate diagnosis and appropriate medical, surgical or behavioral management.

[Rett syndrome: report of 7 cases]

The authors report the clinical and laboratory findings of seven girls with the diagnosis of Rett syndrome seen at the clinic from August 1978 to October 1988. The patient's age varied from two to ten years and they were followed up for 5 years and 9 months in average. The development milestone started to deteriorate between five and twenty-four months. Acquired microcephaly was present in six patients and three cases had hyperventilation. Generalized tonic-clonic seizures were the most frequent type of seizures (6 patients) beginning between one and seven years and effectively controlled with carbamazepine. The EEG's abnormal findings were spike discharges (5 patients) and paroxysmal high-amplitude theta activity (4 patients). The remaining laboratory tests were unremarkable. The pathogenesis of Rett syndrome has not been determined. The clinical evaluation is intended to contribute to the knowledge of that rather uncommon disease.

Another model for the inheritance of Rett syndrome

The fact that probably less than 1% of Rett syndrome cases are familial speaks in favor of a spontaneous mutation as the most common cause of Rett syndrome. However, the few familial cases (about 10) described in the literature, the elevated consanguinity rate in parents of Rett patients (2.4% vs. 0.5%), and the existence of "formes frustes" in relatives of Rett girls, suggest that inheritance must exist. A model based on a hypothetical form of inheritance, namely allelic and non-allelic metabolic interference, fits almost all available data, as well as the exclusive occurrence in females without increased abortion rate.

Two sisters with Rett syndrome

We present the clinical histories and physical findings of two sisters with Rett syndrome. The physical examination, combined with a review of their medical charts, revealed that both patients met the necessary criteria for the diagnosis of Rett syndrome as defined by the Rett syndrome diagnostic criteria work group. The older sister, currently 25 years of age, is typically affected, whereas the younger sister, currently 22 years of age, is affected with a seizure disorder showing an unusually early onset.

A review of the biochemical pathways studied and abnormalities reported in the Rett syndrome

A review of the current research on selected biochemical pathways and reported abnormalities in the Rett syndrome (RS) is presented. While RS has a clinical course that is similar to known metabolic diseases, consistent abnormal biochemical findings in RS patients have not been identified.

The Rett syndrome in males

Two young males in their thirties are reported with a clinical history and examination indistinguishable from typical females with the Rett syndrome. Both had normal early development. The first patient had a regression by the end of the second year. He was late in walking, had prominent hand-wringing from the age of 4 years, and non-progressive dystonia from the age of 14 years. He is still ambulatory. Seizures which started at the age of 18 months have been easily controlled. The second patient has had a severe seizure disorder since the age of 7 months. In his early teens, he lost ambulation and his height and weight fell below the 2nd percentile. He has severe foot dystonia without spasticity. Both patients have a normal head size and no evidence of atrophy on a CT scan of the brain. Both had kyphoscoliosis in their teens. It is difficult to evaluate the incidence of such cases. Little attention being paid to the normal early development, they hide behind vague diagnoses such as cerebral palsy, static encephalopathy, and behavior disorder. Dystonia is often confused with spasticity, the lack of paralysis is not appreciated, apraxia and hand wringing are assumed to be self-stimulatory behaviors.

Multi-institutional survey of the Rett syndrome in Japan

The results of the first multi-institutional survey of the Rett syndrome in Japan are reported. The survey was performed during 1985 and 1986. Eighty-nine cases were collected, of which 54 cases were confirmed to have the Rett syndrome. The ages of the patients ranged between 1 and 26 years. The clinical onsets occurred after 18 months of age in 28 cases, and before the age of one year in 26. No familial cases nor consanguinity was found. The incidence of perinatal abnormalities among the patients was not significantly higher than in other diseases in which no perinatal factors are involved.

Abnormalities of carbohydrate metabolism and of OCT gene function in the Rett syndrome

The pathogenetic basis of the Rett syndrome (RS) is unknown: an X-linked dominant, male-lethal gene defect is thought likely. We present a girl with RS who has defects both of the urea cycle and of carbohydrate metabolism resulting in fasting hypoglycaemia, post-prandial hyperlactataemia and excess urinary orotic acid excretion after alanine load. Her sister has a similar clinical picture, but less marked metabolic anomalies. The mother of these sisters has abnormal urinary orotic acid excretion; she transmitted opposite ornithine carbomoyltransferase (OCT) alleles to the two girls. Another girl with RS has similar metabolic responses to fasting and to carbohydrate load. We conclude that RS may be an aetiologically homogeneous condition, but that it includes a variable pattern of metabolic anomalies, and that the gene defect is distinct from the OCT locus.

Rett syndrome and associated movement disorders

Rett syndrome, a progressive neurodegenerative disorder described only in female subjects, is manifested by a wide spectrum of behavioral and motor abnormalities. We studied 32 patients with this disorder, ages 30 months to 28 years old, and characterized their extrapyramidal disturbance. The most common motor abnormalities were stereotyped movements and gait disturbance, seen in all patients. Bruxism, oculogyric crises, parkinsonism, and dystonia were also common, but myoclonus and choreoathetosis were seen only infrequently. The hyperkinetic movement disorders tended to dominate in younger patients, while bradykinetic disorders were more evident in the older patients. This study provides evidence that movement disorders seen in Rett syndrome reflect age-related neurodegenerative changes in the basal ganglia.

Anaesthesia and Rett syndrome: a case report

Rett syndrome is a neurological disorder of females characterized by dementia, autism, movement disorders and an abnormality of respiratory control. A 14-year-old girl with Rett Syndrome underwent spinal fusion surgery under general anaesthesia. No exacerbation of the respiratory control defect with surgery and anaesthesia was observed. Hypothermia, ongoing blood loss and a normal anion gap acidosis were encountered, but were not attributable to features of this disorder.

Hair copper and zinc concentrations in the Rett syndrome

The hair copper and zinc concentrations in patients with the Rett syndrome in 9 hospitals or institutions, and female age-matched controls were investigated. The copper and zinc concentrations in the 23 patients were 15.1 +/- 3.6 and 177 +/- 20 micrograms/g dry weight (mean +/- SD), respectively, and those in the 22 controls were 14.7 +/- 3.4 and 181 +/- 22, respectively. No significant differences were detected between the copper or zinc concentrations in the patients and controls. The copper and zinc concentrations did not change with age, or the hospital or institution. The ratio of the copper and zinc concentrations was also constant. We conclude that the hair copper and zinc concentrations in patients with the Rett syndrome are the same as those in controls.

Neurophysiological findings in the Rett syndrome, I: EMG, conduction velocity, EEG and somatosensory-evoked potential studies

Nine girls, aged 10 to 22 years, with confirmed Rett syndrome--eight as stage IV and one at stage III--were investigated neurophysiologically. EMG and neurography studies were performed, and somatosensory-evoked responses (SER) were recorded as well as EEG with topographic mapping. Even in advanced clinical stages, no major motor root involvement or demyelinating motor peripheral neuropathy was detected on EMG or neurography, but an axonopathy, possibly of secondary origin, was observed. EEG showed slowing and dominance of low frequency activity of subcortical origin, with or without epileptic discharges. SER findings suggested involvement of the spinal cord and the spinothalamic system. Neurophysiological investigations can be used by the clinician in the differential diagnosis of the Rett syndrome.

Rett syndrome: review and discussion of current diagnostic criteria

Rett syndrome is a mental retardation syndrome that occurs only in females and consists of normal pre-, peri-, and neonatal growth and development. It is followed by rapid neurobehavioral deterioration in late infancy or early childhood, a developmental arrest, plateauing, and then either a course of retarded development or continued deterioration. The period of rapid neuro-behavioral deterioration manifests as a partial autistic syndrome, with loss of production and comprehension of language, hyperactivity, hyperventilation, hand-wringing, and ataxic gait. Current diagnostic criteria are discussed and suggestions for further research are presented.

Rett syndrome in monozygotic twins

The evolution of the Rett syndrome in 29-year-old twin girls is presented. Evidence for monozygosity is given together with a brief account of the problems these girls posed to their family in early childhood.

Rett syndrome in China: report of 9 patients

This is the first report of Rett syndrome in China. Clinical and laboratory data were obtained from 9 girls with Rett syndrome. In addition to the previously reported clinical manifestations (i.e., early deterioration of intelligence, microcephaly, peculiar stereotypic hand movements, and epilepsy), 2 other features were observed in these patients: abnormal evoked response audiometry and low content of the elements, copper and zinc in the hair. The cause of these associated phenomena is unknown.

The clinical recognition and differential diagnosis of Rett syndrome

Rett syndrome (RS) is characterized by progressive loss of intellectual functioning and fine and gross motor skills as well as development of stereotypic hand movement abnormalities, occurring after 6 to 18 months of normal development. Rett syndrome has been previously reported only in girls, but the possibility of the syndrome existing in male children cannot be currently excluded. Although the syndrome is thought to be relatively common, it was only described in the English literature 5 years ago. There is currently no marker for the syndrome; diagnosis is based on clinical criteria. The newly developed diagnostic criteria for RS are reviewed, with special attention given to the historical aspects of the diagnosis in the prenatal, perinatal, neonatal, and early childhood periods. Rett syndrome is characterized by a predictable, orderly progression of signs and symptoms. Four stages of RS have been described; each stage has special characteristics and offers different diagnostic challenges for the neurologist. Infantile autism is the most common incorrect diagnosis made for children with RS. The simultaneous regression of both motor and language skills, as well as the stereotypic hand movements, hyperventilation, bruxism, and seizures in early childhood are all typical in RS and help distinguish RS from infantile autism.

Rett syndrome--a review and discussion of syndrome delineation and syndrome definition

The current status of clinical genetic and pathogenetic knowledge in Rett syndrome is reviewed and updated. Some of the concepts which are highlighted include among others, casual homogeneity vs heterogeneity; the difficulty of dealing with potential variability while the possibility of heterogeneity still exists; progress in examining genetic hypotheses. We review our experience with 8 new patients, note the evidence for the presence of congenital hypotonia in all and several instances of minor anomalies and again raise the issue of whether girls with the Rett syndrome are in fact normal from the time of birth and in early infancy until the characteristic phenotype is recognizable. Previous recommendations for standardized international history, examination and investigation protocols are strongly reinforced, and the question as to who should study brains of Rett syndrome patients is raised by a parent. As is the case in most conditions now being studied by molecular geneticists, finding a marker will be a major etiologic breakthrough, but the work of delineating the pathogenesis will remain to be done.

Rett syndrome: epidemiology and nosology--progress in knowledge 1986--a conference communication

Recent progress from pooled clinical experience is reviewed. The approximate number of documented cases of Rett syndrome (RS) as of October 1986 was 1,100. Three sister pairs, 3 monozygotic twin pairs (both twin girls affected), 3 dizygotic twin pairs (one twin girl affected) are known. Genetics are discussed based on these and other known occurrences. Early seizure-onset variants have been reported in a dozen cases representing various countries. Approximately 20 incomplete RS related cases, also termed "formes frustes," are documented as of October 1986. An actual Swedish series of 66 classical RS, 4 "formes frustes," 2 early seizure-onset variants and 9 other clinically near related atypical cases is summarized. A suggested late stage IV spinal cord impairment is discussed, as well as the whole adult multifacetted complex neurological pattern. Gastrointestinal pathology is discussed with reference to possible generalized neuropeptide disturbances.

Brain stem and spinal cord impairment in Rett syndrome: somatosensory and auditory evoked responses investigations

Six females with Rett syndrome (RS)--all seriously motor disabled with clinical symptomatology indicating not only brain but also spinal cord impairment--were investigated using auditory and somatosensory evoked responses techniques. In all patients the responses representing the pathways through the upper spinal cord were delayed suggesting an impairment of the central conduction time. The findings mean an involvement of the sub-cortical structures, the brain stem and the cervical spinal cord in the disease process. From the natural clinical course and the present findings, it is concluded that RS is also characterized by spinal cord impairment appearing with increasing age and stage of diseases.

A set of monozygotic twins with Rett syndrome

The case history of a set of twins with Rett syndrome is presented. The twins test as monozygotic by both blood groups and HLA titers. In a previous generation, the family had three females who died of an unknown degenerative disease on the paternal side of this family. The discussion includes a hypothesis about female genetic disease occurring in a recessive pattern on the X chromosome.