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Missense MECP2 variants can have various phenotypic effects ranging from a normal phenotype to typical Rett syndrome (RTT). In females, the phenotype can also be influenced by the X-inactivation pattern. In this study, we present detailed clinical descriptions of six patients with a rare base-pair substitution affecting Arg309 at the C-terminal end of the transcriptional repression domain (TRD). All patients have intellectual disability and present with some RTT features, but they do not fulfill the clinical criteria for typical or atypical RTT. Most of the patients also have mild facial dysmorphism. Intriguingly, the mother of an affected male patient is an asymptomatic carrier of this variant. It is therefore likely that the p.(Arg309Trp) variation does not necessarily lead to male lethality, and it results in a wide range of clinical features in females, probably influenced by different X-inactivation patterns in target tissues.

Deletions within 11q12.3-11q13.1 are very rare and to date only two cases have been described in the literature. In this study we describe a 23-year-old male patient with intellectual disability, behavioral problems, dysmorphic features, dysphagia, gastroesophageal reflux and skeletal abnormalities. Cornelia de Lange syndrome (CdLS, OMIM #122470; #300590; #610759; #300882; #614701) was suggested as a differential diagnosis in childhood although he lacked some of the features typical for this disorder. He does not have a mutation in any of the five known CdLS genes (NIPBL, SMC1A, SMC3, HDAC8, RAD21), but a 1.6Mb deletion at chromosome region 11q12.3-11q13.1 was detected by chromosome microarray. The deletion contains several genes including PPP2R5B, which has been associated with intellectual disability and overgrowth; NRXN2, which has been associated with intellectual disability and autism spectrum disorder; and CDCA5, which is part of the cohesin pathway, as are all the five known CdLS genes. It is therefore possible that deletion of CDCA5 may account for some of the CdLS like features of the present case.

Background Neurotrophic factors are essential regulators of neuronal maturation including synaptic synthesis. Among those, Brain derived neurotrophic factor (BDNF) has been in particular focus in the understanding of autism spectrum disorders (ASD). Purpose The aim of our study was to investigate whether BNDF could be used as diagnostic/biological marker for ASD. For this purpose we examined the plasma levels of BDNF and the precursors pro- BDNF in patients with ASD and compared it with non-autistic controls; determined whether there was a correlation between the BDNF and proBDNF levels and clinical severity. We also investigated the coding region of BDNF identify for well-variations which could be associated to ASD. Methods The 65 ASD patients (51 boys) were enrolled from a recent completed epidemiological survey covering two counties (Oppland and Hedmark) in Norway. The mean age of the total number of children who participated in this study was 11,7 years. 30 non-autistic children were included as controls, 14 boys and 16 girls. The mean age was 11.3 years. Exclusion criteria for control group were individuals suffering from either neurological, endocrine, or immune insuffiency. Results and conclusions Patients with ASD were characterized by moderately but significantly elevated plasma levels of BDNF compared to matched controls. No differences were observed in the proBDNF level between patients and controls. Within the ASD group, children with intellectual disability demonstrated increased BDNF, but not proBDNF levels, while the presence of ADHD had no impact on circulating proBDNF or BDNF. No further associations between plasma proBDNF or BDNF and other clinical demographics were observed.

Fragile X syndrome (FXS) is one of the most common causes of intellectual disability/developmental delay (ID/DD), especially in males. It is caused most often by CGG trinucleotide repeat expansions, and less frequently by point mutations and partial or full deletions of the FMR1 gene. The wide clinical spectrum of affected females partly depends on their X-inactivation status. Only few female ID/DD patients with microdeletions including FMR1 have been reported. We describe 3 female patients with 3.5-, 4.2- and 9.2-Mb de novo microdeletions in Xq27.3-q28 containing FMR1. X-inactivation was random in all patients, yet they presented with ID/DD as well as speech delay, macrocephaly and other features attributable to FXS. No signs of autism were present. Here, we further delineate the clinical spectrum of female patients with microdeletions. FMR1 expression studies gave no evidence for an absolute threshold below which signs of FXS present. Since FMR1 expression is known to be highly variable between unrelated females, and since FMR1 mRNA levels have been suggested to be more similar among family members, we further explored the possibility of an intrafamilial effect. Interestingly, FMR1 mRNA levels in all 3 patients were significantly lower than in their respective mothers, which was shown to be specific for patients with microdeletions containing FMR1.

Microscopically visible rearrangements of chromosome 4p includes the two well known abnormalities: partial trisomy 4p, and deletions of the Wolf-Hirschhorn critical regions 1 and 2 (WHSCR 1 and WHSCR2, respectively), which cause well-defined phenotypes including minor anomalies, and developmental delay/intellectual disability. In contrast small duplications of 4p are rare but with the advent of microarray techniques a few cases have been reported in recent years. Here we describe a 3 Mb duplication at 4p16.3 segregating with a characteristic phenotype, macrocephaly, speech delay and mild intellectual disability in a three generation family.

We report on an intellectually disabled girl with a de novo satellited chromosome 10 (10qs) and performed a review of the literature of the non-acrocentric satellited chromosomes (NASC). Satellites and stalks normally occur on the short arms of acrocentric chromosomes; however, the literature cites several reports of satellited non-acrocentric chromosomes, which presumably result from a translocation with an acrocentric chromosome. This is, to our knowledge, the third report of a 10qs chromosome. The phenotype observed in the proband prompted a search for a structural rearrangement of chromosome 10q. By microsatellite analysis we observed a 4 Mb deletion on the long arm of chromosome 10, approximately 145 kb from the telomere. FISH and array CGH analyses revealed a complex rearrangement involving in range from the centromere to the telomere: A 9.64 Mb 10q26.11–q26.2 duplication, a 1.3 Mb region with no copy number change, followed by a 5.62 Mb 10q26.2–q26.3 deletion and a translocation of satellite material. The homology between the repeat sequences at 10q subtelomere region and the sequences on the acrocentric short arms may explain the origin of the rearrangement and it is likely that the submicroscopic microdeletion and microduplication are responsible for the abnormal phenotype in our patient. The patient presented here, with a 15-year follow-up, manifests a distinct phenotype different from the 10q26 pure distal monosomy and trisomy syndromes. © 2011 Wiley Periodicals, Inc.

Low bone mass is reported in growth-retarded patients harboring mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene causing Rett syndrome (RTT). We present the first study addressing both bone mineral density (BMD) and bone size in RTT. Our object was to determine whether patients with RTT do have low BMD when correcting for smaller bones by examination with dual-energy X-ray absorptiometry (DXA). We compared areal BMD (aBMDspine and aBMDtotal hip) and volumetric bone mineral apparent density (vBMADspine and vBMADneck) in 61 patients and 122 matched healthy controls. Further, spine and hip aBMD and vBMAD of patients were associated with clinical risk factors of low BMD, low-energy fractures, MECP2 mutation groups, and X chromosome inactivation (XCI). Patients with RTT had reduced bone size on the order of 10% and showed lower values of spine and hip aBMD and vBMAD ( p < .001) adjusted for age, pubertal status, and body mass index (BMI). aBMDspine, vBMADspine, and aBMDtotal hip were associated with low-energy fractures ( p < .05). Walking was significantly associated to aBMDtotal hip and vBMADneck adjusted for age and body mass index (BMI). Further, vBMADneck was significantly associated to a diagnosis of epilepsy, antiepileptic treatment, and MECP2 mutation group, but none of the associations with vBMADneck remained clinically significant in a multiple adjusted model including age and BMI. Neither aBMDspine, vBMADspine, nor aBMDtotal hip were significantly associated with epilepsy, antiepileptic treatment, MECP2 mutation group, XCI, or vitamin D status. Low bone mass and small bones are evident in RTT, indicating an apparent low-bone-formation phenotype. 2011 American Society for Bone and Mineral Research.

Silver–Russell syndrome (SRS) is characterised by prenatal and postnatal growth retardation, dysmorphic facial features, and body asymmetry. In 35–60% of SRS cases the paternally methylated imprinting control region (ICR) upstream of the H19 gene (H19-ICR) is hypomethylated, leading to downregulation of IGF2 and bi-allelic expression of H19 . H19 and IGF2 are reciprocally imprinted genes on chromosome 11p15. The expression is regulated by the imprinted methylation of the ICR, which modulates the transcription of H19 and IGF2 facilitated by enhancers downstream of H19 . A promoter element of IGF2 , IGF2P0, is differentially methylated equivalently to the H19-ICR, though in a small number of SRS cases this association is disrupted—that is, hypomethylation affects either H19-ICR or IGF2P0. Three pedigrees associated with hypomethylation of IGF2P0 in the probands are presented here, two with paternally derived deletions, and one with a balanced translocation of inferred paternal origin. They all have a breakpoint within the H19 / IGF2 enhancer region. One proband has severe growth retardation, the others have SRS. This is the first report of paternally derived structural chromosomal mutations in 11p15 causing SRS. These cases define a novel aetiology of the growth retardation in SRS, namely, dissociation of IGF2 from its enhancers.

Usher syndrome (USH) is the most common genetic disease that causes both deafness and blindness. USH is divided into three types, USH1, USH2 and USH3, depending on the age of onset, the course of the disease, and on the degree of vestibular dysfunction. By homozygosity mapping of a consanguineous Danish family of Dutch descent, we have identified a novel locus for a rare USH3-like syndrome. The affected family members have a unique association of retinitis pigmentosa, progressive hearing impairment, vestibular dysfunction, and congenital cataract. The phenotype is similar, but not identical to that of USH3 patients, as congenital cataract has not been reported for USH3. By homozygosity mapping, we identified a 7.3 Mb locus on chromosome 15q22.2-23 with a maximum multipoint LOD score of 2.0. The locus partially overlaps with the USH1 locus, USH1H, a novel unnamed USH2 locus, and the non-syndromic deafness locus DFNB48.

We aimed to improve the understanding of genotype-phenotype correlations in Rett syndrome (RS) by adopting a novel approach to categorising phenotypic dimensions - separating typicality of presentation, outcome severity and age of onset - and by classifying MECP2 mutations strictly by predicted functional attributes. MECP2 mutation screening results were available on 190 patients with a clinical diagnosis of RS (140 cases with classic RS, 50 with atypical RS). 135 cases had identified mutations. Of the 140 patients, 116 with classic RS (82.9%) had an identified mutation compared with 19 of 50 patients (38%) with an atypical presentation. Cases with early onset of regression and seizures, and those with clinical features that might indicate alternative aetiologies, were less likely to have mutations. Individuals with late truncating mutations had a less typical presentation than cases with missense and early truncating mutations, presumably reflecting greater residual function of MECP2 protein. Individuals with early truncating mutations had a more severe outcome than cases with missense and late truncating mutations. These findings held when restricting the analysis to cases over 15 years of age and classic cases only. Previous findings of variation in severity among the common mutations were confirmed. The approach to phenotypic and genotypic classification adopted here allowed us to identify genotype-phenotype associations in RS that may aid our understanding of pathogenesis and also contribute to clinical knowledge on the impact of different types of mutations.

Mutations in the CDKL5 gene (also known as STK9) have recently been shown to cause early onset epilepsy and severe mental retardation (ISSX or West syndrome). Patients with CDKL5 mutations sometimes also show features similar to those seen in Rett Syndrome (RTT). We have screened the CDKL5 gene in 94 patients with RTT or a RTT-like phenotype who had tested negative for MECP2 mutations (13 classical RTT female subjects, 25 atypical RTT female subjects, 40 RTT-like female and 16 RTT-like male subjects; 33 of the patients had early onset seizures). Novel pathogenic CDKL5 mutations were identified in three girls, two of whom had initially been diagnosed with the early onset seizure variant of RTT and the other with early onset seizures and some features of RTT. In addition, the 33 patients with early seizures were screened for the most common mutations in the ARX gene but none were found. Combining our three new cases with the previously published cases, 13/14 patients with CDKL5 mutations presented with seizures before the age of 3 months.

In 1999, mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2) were first reported in patients with Rett syndrome (RTT). The MECP2 gene is located at Xq28 and consists of 4 exons. About 80–90 % of the classic RTT patients harbor mutations in the coding region of MECP2, while the molecular cause is unknown in the remaining 10–20%. Several groups have searched for large rearrangements within the MECP2 and the results indicate that a fraction of MECP2-negative RTT cases has large deletions of the MECP2. In this study we have used the Multiplex Ligation-dependent Probe Amplification (MLPA) technique to screen 45 RTT patients, who have previously been tested negative for mutations in the coding region of MECP2. The MECP2-MLPA is a semi-quantitative multiplex PCR approach. It determines the relative number of copies of each MECP2 exon. With this approach we detected seven RTT patients with genomic deletions and further characterized the deletions using real time quantitative PCR (qPCR) and long-range PCR. The seven patients were given a severity score and their X chromosome inactivation profiles were determined in order to identify a possible genotype-phenotype correlation. The results from this study indicate that large deletions in MECP2 cause classic RTT. © 2005 Wiley-Liss, Inc.