Intelligence in individuals with a neurofibromatosis type 1 microdeletion.
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Biomedical subjects
Publications and source records attributed to M J Descheemaeker.
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The Prader-Willi syndrome (PWS) is a genetically determined developmental disorder caused by abnormalities of the proximal region of chromosome 15q11-13. In a previous study, we reported that psychotic episodes, occurring in 16% of persons with PWS, had an onset in adolescence, never occurred in persons with paternal deletion, and were exclusively associated with maternal uniparental disomy (UPD) or imprinting abnormalities (IM). In order to gain a better understanding of the psychopathology and to further refine the psychiatric diagnosis, we describe in more detail the psychopathological manifestations of six adults with a history of psychotic episodes. All these individuals had a detailed psychiatric examination, including the use of the operational criteria (OPCRIT) checklist. An identifiable subtype of psychotic disorder was associated with PWS. Characteristics include early age of onset, acute onset, polymorphous, and shifting symptomatology and a need for psychiatric hospitalization. The presence of precipitating stress factors and a prodromal phase with physiological symptoms was reported in all patients. Current diagnostic categories do not allow an unequivocal psychiatric diagnosis.
The personality profile of 44 youngsters (24 males, 20 females; mean age 11 years, 3 months) with neurofibromatosis type 1 (NF1) was compared with a group of 220 non-NF1 control youngsters (matched on age and gender). Personality characteristics of each youngster were rated by both parents, using the California Child Q-set (CCQ); [Block and Block, 1980]. The scores on eight personality dimensions were compared, i.e., Extraversion, Agreeableness, Conscientiousness, Emotional Stability, Openness, Motor Activity, Irritability, and Dependency. Moreover, personality of NF1 youngsters was related to IQ level, severity of medical problems, the presence or absence of visible cosmetic disfiguring, and de novo versus familial origin of NF1. The personality profile of NF1 youngsters was markedly different from the non-NF1 youngsters. Compared to the 220 control children, they were equally agreeable, but less conscientious, less emotionally stable, less open for new experience, with less motor activity, and more extravert, more dependent, and more irritable. Personality characteristics were similar for children with maternally or paternally inherited NF1, or for children with a new mutation. There was no association with gender, the severity of medical and cosmetic problems, and IQ.
Prader-Willi syndrome (PWS) is a genetic disorder caused by the loss of the paternal contribution of the proximal part (15q11-q13) of the long arm of chromosome 15 (i.e. deletion, disomy and imprinting mutation). The syndrome is associated with distinct physical dysmorphism, as well as with specific behavioural and psychopathological characteristics. Psychiatric symptoms in adolescence and adulthood have been described, including acute cycloid psychosis, and obsessive compulsive, bipolar and pervasive developmental disorders. At the Centre for Human Genetics in Leuven, Belgium, 53 individuals (31 children and adolescents, and 22 adults) have been followed up for 15 years by a special multidisciplinary team. Attention was given to their medical, cognitive, behavioural and emotional development, and the evolution of psychiatric disorders in adolescence and adulthood. This study describes the psychiatric problems in four patients diagnosed with acute cycloid psychosis and traces their development from infancy to adolescence. Four other individuals needed psychiatric evaluation and treatment, and could be diagnosed as having unspecified bipolar disorder, also termed unstable mood disorder. Both groups were compared, and significant differences in early development and later evolution into adulthood were noted. The individuals with PWS who later developed psychotic episodes were described as active and extrovert toddlers, and showed autistic behaviour during their primary school education. Their intellectual functioning was in the moderate to severely retarded range. The individuals with PWS who later developed an unstable mood disorder were described as rather passive and introvert toddlers, and they presented less disturbed behaviour during their primary school education. The intellectual functioning of these subjects was in the normal to borderline range.
Angelman syndrome (AS) is a distinct neurogenetic disorder and the phenotype is well known in childhood and adolescence. However, with advancing age the clinical and behavioral phenotype changes. In adulthood, the phenotype can be rather aspecific. We report on AS in 3 severely to profoundly mentally retarded patients, who developed severe neurologic complications of severe tremor, spasticity and coordination problems, resulting into severe loss of function. They presented atypical craniofacial features, short stature, epileptic seizures, microcephaly, brachytelephalangy and absent speech. Two patients presented at an older age a change in day-night rhythm. Based on this experience, we conclude that all severely to profoundly mentally retarded patients with atypical phenotype, spasticity, absent speech, epileptic seizures and changed day-night rhythm are candidates for further cytogenetic and molecular investigation for AS. Clinical photographs of the patient at a younger age can be helpful. The presence of the typical EEG pattern with frontal triphasic delta waves may direct to the diagnosis of AS.
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In a group of 28 children with neurofibromatosis type 1 aged between 4 and 16 years, neuroradiological findings were correlated with intelligence as measured by the Wechsler scales. The presence or specific location in the brain of T2 weighted prolonged signals on MRI was not associated with cognitive problems. No other physical characteristics associated with neurofibromatosis type 1 were found to correlate significantly with IQ. At the present these T2 weighted hyper-intense spots should not be used to predict neurofibromatosis type 1 associated cognitive problems.
The authors review the present data on the clinical and molecular aspects of neurofibromatosis type 1 (NF1). In the clinical part attention is given to the frequent observation of learning disabilities in NF1 children. In these children visual-spatial integration deficits and an increased incidence of school performance problems are observed. The NF1 gene is located on chromosome 17 (17q11.2), and is highly conserved across species. Up to now only a limited number of mutations in this gene have been characterized, and this shows a general lack of genotype-phenotype correlation. Evidence is given that the NF1 gene acts as a true tumor suppressor gene and that oncogenesis in NF1 is a complex multistep phenomenon with the second hit in the NF1 gene as the initiating event. The importance of specialized multidisciplinary outpatient clinics for neurofibromatosis is emphasized because of the complexity of follow-up and treatment of these patients.
The Prader-Willi syndrome is characterized by four cardinal symptoms i.e. hypotonia, hypogonadism, mental retardation and extreme obesity. Behavioural and psychological problems are frequent in these patients, mostly related to the withholding of food and the necessity of diet control. A treatment program has been developed for their eating problems. The treatment program is based on three points: 1. The importance of teaching them healthy eating habits within a specific eating culture. 2. The convinction that their obsession and fixation on food can be canalized and satisfied by being occupied, by playing and by learning about food. 3. The opinion that involvement and active participation in their diet is necessary to prevent behavioural problems and to stimulate "self control". The key objective of this program are to control the weight gain and to prevent behavioural problems. Based on these two main objectives, we developed a program based on four principles: a personal low calorie diet, the principles of behaviour modification, stimulation of motor skills and other developmental areas, and parental participation and education. This program is applied in group situation and in individual cases. The results of the present study in 4 children are encouraging. We noted an average weight loss of 2.25 kg, with an average increase of height of 3.5 cm. On intelligence testing we found that the scores on the performal subtests improved while the scores on the verbal subtests decreased. Little change occurred in the behavioural profile.
Developmental testing (7 children, aged between 17 months and 4 years) and intelligence profile analysis (38 children, aged between 4 and 16 years) were performed in a group of 45 children with NF1 followed at the Leuven NF clinic. Mental retardation (total IQ < 70) was noted in 2 of the 38 children between 4 and 16 years (5.2%). The mean total IQ of this group was 89.9 with a significantly higher verbal IQ than performed IQ. Factor analysis according to Kaufman showed a significantly weaker score on perceptual organization as compared with verbal comprehension. Concentration difficulty as measured by the Freedom from Distractibility Factor of Kaufman was not an important problem in the total group of children, but was more significant in the group of children with a total IQ above 85. Subtest analysis also showed significantly better scores on some verbal comprehensive tests as compared with some perceptual organization tests. Learning disabilities were frequent in the children analyzed in this report and non-verbal learning disabilities were the predominant type (40% of children). However other types and combinations of different types of learning disabilities were also found.