Case report: A novel de novo IGF2 missense variant in a Finnish patient with Silver-Russell syndrome.

Silver-Russell syndrome (SRS, OMIM 180860) is a rare imprinting disorder characterized by intrauterine and postnatal growth restriction, feeding difficulties in early childhood, characteristic facial features, and body asymmetry. The molecular cause most commonly relates to hypomethylation of the imprinted 11p15.5 IGF2/H19 domain but remains unknown in about 40% of the patients. Recently, heterozygous paternally inherited pathogenic variants in IGF2, the gene encoding insulin-like growth factor 2 (IGF2), have been identified in patients with SRS. We report a novel de novo missense variant in IGF2 (c.122T > G, p.Leu41Arg) on the paternally derived allele in a 16-year-old boy with a clinical diagnosis of SRS. The missense variant was identified by targeted exome sequencing and predicted pathogenic by multiple in silico tools. It affects a highly conserved residue on a domain that is important for binding of other molecules. Our finding expands the spectrum of disease-causing variants in IGF2. Targeted exome sequencing is a useful diagnostic tool in patients with negative results of common diagnostic tests for SRS.

Mosaic Deletions of Known Genes Explain Skeletal Dysplasias With High and Low Bone Mass.

Mosaicism, a state in which an individual has two or more genetically distinct populations of cells in the body, can be difficult to detect because of either mild or atypical clinical presentation and limitations in the commonly used detection methods. Knowledge of the role of mosaicism is limited in many skeletal disorders, including osteopathia striata with cranial sclerosis (OSCS) and cleidocranial dysplasia (CCD). We used whole-genome sequencing (WGS) with coverage >40× to identify the genetic causes of disease in two clinically diagnosed patients. In a female patient with OSCS, we identified a mosaic 7-nucleotide frameshift deletion in exon 2 of AMER1, NM_152424.4:c.855_861del:p.(His285Glnfs*7), affecting 8.3% of the WGS reads. In a male patient with CCD, approximately 34% of the WGS reads harbored a 3710-basepair mosaic deletion, NC_000006.11:g.45514471_45518181del, starting in intron 8 of RUNX2 and terminating in the 3' untranslated region. Droplet digital polymerase chain reaction was used to validate these deletions and quantify the absolute level of mosaicism in each patient. Although constitutional variants in AMER1 and RUNX2 are a known cause of OSCS and CCD, respectively, the mosaic changes here reported have not been described previously. Our study indicates that mosaicism should be considered in unsolved cases of skeletal dysplasia and should be investigated with comprehensive and sensitive detection methods. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Segmental and total uniparental isodisomy (UPiD) as a disease mechanism in autosomal recessive lysosomal disorders: evidence from SNP arrays.

Analyses in our diagnostic DNA laboratory include genes involved in autosomal recessive (AR) lysosomal storage disorders such as glycogenosis type II (Pompe disease) and mucopolysaccharidosis type I (MPSI, Hurler disease). We encountered 4 cases with apparent homozygosity for a disease-causing sequence variant that could be traced to one parent only. In addition, in a young child with cardiomyopathy, in the absence of other symptoms, a diagnosis of Pompe disease was considered. Remarkably, he presented with different enzymatic and genotypic features between leukocytes and skin fibroblasts. All cases were examined with microsatellite markers and SNP genotyping arrays. We identified one case of total uniparental disomy (UPD) of chromosome 17 leading to Pompe disease and three cases of segmental uniparental isodisomy (UPiD) causing Hurler-(4p) or Pompe disease (17q). One Pompe patient with unusual combinations of features was shown to have a mosaic segmental UPiD of chromosome 17q. The chromosome 17 UPD cases amount to 11% of our diagnostic cohort of homozygous Pompe patients (plus one case of pseudoheterozygosity) where segregation analysis was possible. We conclude that inclusion of parental DNA is mandatory for reliable DNA diagnostics. Mild or unusual phenotypes of AR diseases should alert physicians to the possibility of mosaic segmental UPiD. SNP genotyping arrays are used in diagnostic workup of patients with developmental delay. Our results show that even small Regions of Homozygosity that include telomeric areas are worth reporting, regardless of the imprinting status of the chromosome, as they might indicate segmental UPiD.

A novel transthyretin Lys70Glu (p.Lys90Glu) mutation presenting with vitreous amyloidosis and carpal tunnel syndrome.

OBJECTIVE: We describe a novel TTR mutation with vitreous opacities and carpal tunnel syndrome. MATERIALS AND METHODS: A 78 year-old woman with vitreous opacities, her daughter with dry eye syndrome, and brother with carpal tunnel syndrome were tested for a mutation in the TTR gene. The vitreous opacities were removed and stained with Congo red and immunohistochemistry against wild type TTR. Skin and gut biopsies and specimens of soft tissue were examined histopathologically. Leukocyte DNA from the proband was analysed by direct sequencing of exons 1 to 4 of the TTR gene and DNA from her daughter and brother using segregation analysis. RESULTS: A point mutation c.268 A>C, in the TTR gene, leading to a missense mutation p.Lys90Glu was found in all subjects. The vitreous opacities were pearl string-like. Histopathology showed red to green birefringence in Congo red, typical to amyloid, and the specimens were immunoreactive with antibodies against TTR. CONCLUSION: We present a novel autosomally inherited Lys90Glu mutation in the TTR gene. This is the first reported FAP family with this mutation in Finland.

Deletion of TOP3ß, a component of FMRP-containing mRNPs, contributes to neurodevelopmental disorders.

Implicating particular genes in the generation of complex brain and behavior phenotypes requires multiple lines of evidence. The rarity of most high-impact genetic variants typically precludes the possibility of accruing statistical evidence that they are associated with a given trait. We found that the enrichment of a rare chromosome 22q11.22 deletion in a recently expanded Northern Finnish sub-isolate enabled the detection of association between TOP3B and both schizophrenia and cognitive impairment. Biochemical analysis of TOP3ß revealed that this topoisomerase was a component of cytosolic messenger ribonucleoproteins (mRNPs) and was catalytically active on RNA. The recruitment of TOP3ß to mRNPs was independent of RNA cis-elements and was coupled to the co-recruitment of FMRP, the disease gene product in fragile X mental retardation syndrome. Our results indicate a previously unknown role for TOP3ß in mRNA metabolism and suggest that it is involved in neurodevelopmental disorders.

High-resolution SNP array analysis of patients with developmental disorder and normal array CGH results.

BACKGROUND: Diagnostic analysis of patients with developmental disorders has improved over recent years largely due to the use of microarray technology. Array methods that facilitate copy number analysis have enabled the diagnosis of up to 20% more patients with previously normal karyotyping results. A substantial number of patients remain undiagnosed, however. METHODS AND RESULTS: Using the Genome-Wide Human SNP array 6.0, we analyzed 35 patients with a developmental disorder of unknown cause and normal array comparative genomic hybridization (array CGH) results, in order to characterize previously undefined genomic aberrations. We detected no seemingly pathogenic copy number aberrations. Most of the vast amount of data produced by the array was polymorphic and non-informative. Filtering of this data, based on copy number variant (CNV) population frequencies as well as phenotypically relevant genes, enabled pinpointing regions of allelic homozygosity that included candidate genes correlating to the phenotypic features in four patients, but results could not be confirmed. CONCLUSIONS: In this study, the use of an ultra high-resolution SNP array did not contribute to further diagnose patients with developmental disorders of unknown cause. The statistical power of these results is limited by the small size of the patient cohort, and interpretation of these negative results can only be applied to the patients studied here. We present the results of our study and the recurrence of clustered allelic homozygosity present in this material, as detected by the SNP 6.0 array.

[Update on current care guidelines: appropriate treatment of medical problems associated with Down's syndrome]. / Downin oireyhtymään liittyvien lääketieteellisten ongelmien hyvä hoito.

The lifetime prognosis of people with Down's syndrome has improved. Development of the services that health care and society can offer to such people is ongoing. These guidelines are targeted at defining what is required to further increase the lifespan and quality-of-life of people with Down's syndrome.

Epilepsy caused by CDKL5 mutations.

Mutations in the cyclin-dependent kinase-like 5 gene (CDKL5) have been identified in female patients with early onset epileptic encephalopathy and severe mental retardation with a Rett-like phenotype. Subsequently CDKL5 mutations were shown to be associated with more diverse phenotypes including mild epilepsy and autism without epilepsy. Furthermore, CDKL5 mutations were found in patients with Angelman-like phenotype. The severity of epilepsy associated with CDKL5 mutations was recently shown to correlate with the type of CDKL5 mutations and epilepsy was identified to involve three distinct sequential stages. Here, we describe the phenotype of a severe form of neurodevelopmental disease in a female patient with a de novo nonsense mutation of the CDKL5 gene c.175C > T (p.R59X) affecting the catalytic domain of CDKL5 protein. Mutations in the CDKL5 gene are less common in males and can be associated with a genomic deletion as found in our male patient with a deletion of 0.3 Mb at Xp22.13 including the CDKL5 gene. We review phenotypes associated with CDKL5 mutations and examine putative relationships between the clinical epilepsy phenotype and the type of the mutation in the CDKL5 gene.

Array CGH in molecular diagnosis of mental retardation - A study of 150 Finnish patients.

We report on the results of an array comparative genomic hybridization (array CGH) study of 150 karyotypically normal Finnish patients with idiopathic mental retardation and/or dysmorphic features and/or malformations. Using high-resolution microarray analysis, we sought to identify clinically relevant microdeletions and microduplications in these patients. The results were confirmed using other methods and compared with findings reported in recent publications and internet databases. Small aberrations of potential clinical significance were found in 28 (18.6%) of the 150 patients. Eight of the identified aberrations are known to cause syndromes, 4 affected the X chromosome in males, 4 were familial, and 13 have yet to be associated with a phenotype. This study demonstrates the benefits of array CGH in clinical diagnostics of developmental disorders. Further, our findings give evidence of new syndromes.

Molecular correlates of age-dependent seizures in an inherited neonatal-infantile epilepsy.

Many idiopathic epilepsy syndromes have a characteristic age dependence, the underlying molecular mechanisms of which are largely unknown. Here we propose a mechanism that can explain that epileptic spells in benign familial neonatal-infantile seizures occur almost exclusively during the first days to months of life. Benign familial neonatal-infantile seizures are caused by mutations in the gene SCN2A encoding the voltage-gated Na(+) channel Na(V)1.2. We identified two novel SCN2A mutations causing benign familial neonatal-infantile seizures and analysed the functional consequences of these mutations in a neonatal and an adult splice variant of the human Na(+) channel Na(V)1.2 expressed heterologously in tsA201 cells together with beta1 and beta2 subunits. We found significant gating changes leading to a gain-of-function, such as an increased persistent Na(+) current, accelerated recovery from fast inactivation or altered voltage-dependence of steady-state activation. Those were restricted to the neonatal splice variant for one mutation, but more pronounced for the adult form for the other, suggesting that a differential developmental splicing does not provide a general explanation for seizure remission. We therefore analysed the developmental expression of Na(V)1.2 and of another voltage-gated Na(+) channel, Na(V)1.6, using immunohistochemistry and real-time reverse transcription-polymerase chain reaction in mouse brain slices. We found that Na(V)1.2 channels are expressed early in development at axon initial segments of principal neurons in the hippocampus and cortex, but their expression is diminished and they are gradually replaced as the dominant channel type by Na(V)1.6 during maturation. This finding provides a plausible explanation for the transient expression of seizures that occur due to a gain-of-function of mutant Na(V)1.2 channels.

Chromosomal abnormalities in Finnish orofacial cleft patients: excess of submucous cleft patients?

OBJECTIVE: The aim was to identify chromosomal regions possibly involved in the development of orofacial clefts and to compare syndromic cleft phenotypes with previous reports. DESIGN: We have retrospectively gathered and analyzed chromosomal aberrations and phenotypes of Finnish cleft patients treated at the Cleft and Craniofacial Centre, Helsinki University Central Hospital. SETTING: The study was carried out at the Cleft and Craniofacial Centre, Helsinki University Central Hospital. PATIENTS: The cleft register contains information on about 7600 Finnish cleft patients. MAIN OUTCOME MEASURES: Identification of patients for further molecular analyses and identification of chromosomal regions associated with orofacial clefting. RESULTS: We identified 37 cleft patients with chromosomal aberrations of putative research interest. CONCLUSIONS: We were able to efficiently select patients for further molecular analyses and identify chromosomal regions that might be associated with orofacial clefting. The percentage of submucous cleft patients among cleft patients with chromosomal aberrations was unexpectedly high.

[Microtia--not just an ear problem]. / Mikrotia--ei ainoastaan korvaongelma.

Microtia can be defined as a malformation of the auricle with varying severity. In the majority of patients it is combined with atresia or stenosis of the external auditory canal. The prevalence of microtia in Finland is approx. 4 out of 10000. Associated anomalies should be actively seeked and excluded. Approximately 70% of the patients seem to be non-syndromatic. Patients with microtia are known to more than usual have other structural abnormalities. With the exception of the mildest cases, the development of facial structure and dental occlusion should be monitored in all microtia patients, attempting to actively exclude any associated diseases.

Further evidence for a relationship between the 5p15 chromosome region and the oculoauriculovertebral anomaly.

The oculoauriculovertebral anomaly (OAV) or Goldenhar syndrome is a malformation complex that has been described in several chromosomal rearrangements. Among them a deletion of the terminal 5p has recurred in seven previous patients. We wish to report on an additional such patient in order to reinforce the significance of this genomic region in the cause of at least a subgroup of OAV cases. Future studies, particularly in the OAV patients with a lateral facial cleft, might define one genetic background of the disorder. Our patient had a complex translocation chromosome 45,XX, inv(2) (q32q37)mat, dic(5;21) (p15.3;q22.3)dn, resulting in a terminal 5p deletion, a terminal deletion of 21q demonstrated by FISH studies, and a duplication of 21q22.11-q22.12 documented by molecular karyotyping. In addition to OAV she developed myelodysplasia treated with bone marrow transplantation. We discuss her clinical findings with reference to her karyotype findings and review the patients with OAV and a terminal deletion of 5p.

Molecular analysis of the CHD7 gene in CHARGE syndrome: identification of 22 novel mutations and evidence for a low contribution of large CHD7 deletions.

PURPOSE: Autosomal dominant CHARGE syndrome (OMIM no. 214800) is characterized by choanal atresia or cleft lip or palate, ocular colobomas, cardiovascular malformations, retardation of growth, ear anomalies, and deafness, and is caused by mutations in the CHD7 gene. Here, we describe the outcome of a molecular genetic analysis in 18 Finnish and 56 German patients referred for molecular confirmation of the clinical diagnosis of suspected CHARGE syndrome. METHODS: Quantitative real-time polymerase chain reaction or multiplex ligation-dependent probe amplification assays did not reveal deletions in mutation negative cases, suggesting that larger CHD7 deletions are not a major cause of CHARGE syndrome. RESULTS: In this group of 74 patients, we found mutations in 30 cases. 22 mutations were novel, including 11 frameshift, 5 nonsense, 3 splice-site, and 3 missense mutations. One de novo frameshift mutation was found in the last exon and is expected to result in a minimally shortened CHD7 polypeptide. Because the mutation is associated with a typical CHARGE syndrome phenotype, it may indicate the presence of an as yet unknown functional domain in the very carboxyterminal end of CHD7. CONCLUSIONS: Our mutation detection rate of 40.5% is reflective of screening an unselected sample population referred for CHD7 testing based on suspected clinical diagnosis of CHARGE syndrome and not for having met strict clinical criteria for this disorder.

Inheritance of microtia in the Finnish population.

OBJECTIVE: To study the inheritance of microtia in the Finnish population, identify families for genetic linkage analyses and compare the phenotype between sporadic and familial patients. METHODS: Retrospective case series and patient questionnaire of 109 microtia patients referred for reconstruction of the earlobe to the Helsinki University Central Hospital during the years 1980-2005. RESULTS: 22 out of the 109 patients had a relative with microtia or preauricular tag. The familial and sporadic patients did not differ in microtia phenotype or sex distribution. Urinary system anomalies were statistically more prevalent in familial patients (p<0.01). The analyses of the birthplace of parents or grandparents of familial or sporadic microtia patients resulted in no evidence for founder effect. CONCLUSIONS: The prevalence of familial microtia/OAVS in the Finnish population is higher than 20%. The sporadic and familial microtia/OAVS patients do not differ in the phenotype or sex distribution. The mode of inheritance seems to be autosomal dominant with incomplete penetrance.

Microtia in Finland: comparison of characteristics in different populations.

OBJECTIVE: To compare the characteristics of microtia in Finland and in other populations. METHODS: Retrospective case series and patient questionnaire of 190 microtia patients referred for reconstruction of the earlobe to the Helsinki University Central Hospital during the years 1980-2005. RESULTS: The prevalence in Finland is 4.34/10,000 and varied in other populations from 0.83 to 17.4/10,000. Microtia is seen more in males (58%), as unilateral (88.4%), right-sided (59.5%) and it is almost always associated with aural atresia or stenosis (93%). There is conductive hearing loss in 96% and sensorineural hearing loss in 8% of the affected ears. 11% of the patients had congenital heart defects, and 5% had anomalies of extremities. CONCLUSIONS: There is variation in the prevalence and characteristics of microtia in different populations.

Clinical and mutational spectrum of Mowat-Wilson syndrome.

Mowat-Wilson Syndrome is a recently delineated mental retardation syndrome usually associated with multiple malformations and a recognizable facial phenotype caused by defects of the transcriptional repressor ZFHX1B. To address the question of clinical and mutational variability, we analysed a large number of patients with suspected Mowat-Wilson Syndrome (MWS). Without prior knowledge of their mutational status, 70 patients were classified into "typical MWS", "ambiguous" and "atypical" groups according to their facial phenotype. Using FISH, qPCR and sequencing, ZFHX1B deletions, splice site or truncating mutations were detected in all 28 patients classified as typical MWS. No ZFHX1B defect was apparent in the remaining 15 cases with ambiguous facial features or in the 27 atypical patients. Genotype-phenotype analysis confirmed that ZFHX1B deletions and stop mutations result in a recognizable facial dysmorphism with associated severe mental retardation and variable malformations such as Hirschsprung disease and congenital heart defects. Our findings indicate that structural eye anomalies such as microphthalmia should be considered as part of the MWS spectrum. We also show that agenesis of the corpus callosum and urogenital anomalies (especially hypospadias) are significant positive predictors of a ZFHX1B defect. Based on our observation of affected siblings and the number of MWS cases previously reported, we suggest a recurrence risk of around 1%. The lack of missense mutations in MWS and MWS-like patients suggests there may be other, as yet unrecognized phenotypes, associated with missense mutations of this transcription factor.

The first Finnish patient with the Floating-Harbor syndrome: the follow-up of eight years.

We report the follow-up data on the first Finnish patient with the Floating-Harbor syndrome (FHS) reported by us in 1996 at the age of 6 years (Ala-Mello and Peippo. We also discuss the diagnostic criteria of FHS, with a critical review of the literature.

De novo SCN1A mutations are a major cause of severe myoclonic epilepsy of infancy.

Severe myoclonic epilepsy of infancy (SMEI or Dravet syndrome) is a rare disorder occurring in young children often without a family history of a similar disorder. The earliest disease manifestations are usually fever-associated seizures. Later in life, patients display different types of afebrile seizures including myoclonic seizures. Arrest of psychomotor development occurs in the second year of life and most patients become ataxic. Patients are resistant to antiepileptic drug therapy. Recently, we described de novo mutations of the neuronal sodium channel alpha-subunit gene SCN1A in seven isolated SMEI patients. To investigate the contribution of SCN1A mutations to the etiology of SMEI, we examined nine additional SMEI patients. We observed eight coding and one noncoding mutation. In contrast to our previous study, most mutations are missense mutations clustering in the S4-S6 region of SCN1A. These findings demonstrate that de novo mutations in SCN1A are a major cause of isolated SMEI.