Clinical and mutation data in 12 patients with the clinical diagnosis of Nager syndrome.

Nager syndrome (MIM #154400) is the best-known preaxial acrofacial dysostosis, mainly characterized by craniofacial and preaxial limb anomalies. The craniofacial abnormalities mainly consist of downslanting palpebral fissures, malar hypoplasia, micrognathia, external ear anomalies, and cleft palate. The preaxial limb defects are characterized by radial and thumb hypoplasia or aplasia, duplication of thumbs and proximal radioulnar synostosis. Haploinsufficiency of SF3B4 (MIM *605593), which encodes SAP49, a component of the pre-mRNA spliceosomal complex, has recently been identified as the underlying cause of Nager syndrome. In our study, we performed exome sequencing in two and Sanger sequencing of SF3B4 in further ten previously unreported patients with the clinical diagnosis of Nager syndrome, including one familial case. We identified heterozygous SF3B4 mutations in seven out of twelve patients. Four of the seven mutations were shown to be de novo; in three individuals, DNA of both parents was not available. No familial mutations were discovered. Three mutations were nonsense, three were frameshift mutations and one T > C transition destroyed the translation start signal. In three of four SF3B4 negative families, EFTUD2 was analyzed, but no pathogenic variants were identified. Our results indicate that the SF3B4 gene is mutated in about half of the patients with the clinical diagnosis of Nager syndrome and further support genetic heterogeneity for this condition.

X-linked Aarskog syndrome: report on a novel FGD1 gene mutation. Executive dysfunction as part of the behavioural phenotype.

Aarskog-Scott syndrome [OMIM 100050] is a predominantly X-linked disorder that is phenotypically characterized by short stature, craniofacial dysmorphisms, brachydactyly and urogenital abnormalities. The level of intelligence shows a great variability and no specific behavioural phenotype has been described so far. In about 20 percent ofAarskog families, a mutation in the FGD1 gene located in Xp11.21 can be identified. In the present study, four affected males from the fourth generation of a large Dutch family (published in 1983 by Van de Vooren et al. (41)) are described. A novel FGD1 missense mutation (R402W) at position 1204 (1204C>T) was demonstrated. In the patients, the level of intelligence varied between normal and severely disabled. Their behavioural profile showed, among others, elements of attention deficit hyperactivity disorder, primarily reflected by impaired executive attentional processes that may be sensitive to systematic training.

Undetected anomalies in foetuses with a prenatal diagnosis of isolated cleft.

The aim of this study was to determine the rate of undetected additional anomalies following a prenatal diagnosis of isolated oral cleft. Data of all infants with a prenatal diagnosis of isolated oral cleft born between 2000 and 2015 were studied retrospectively. Additional anomalies detected after birth were categorized as minor or major and included structural and chromosomal anomalies. Isolated clefts of the lip (CL), lip and alveolus (CLA) and lip, alveolus, and palate (CLAP) were diagnosed prenatally in 176 live-born infants. The type of cleft was more extensive after birth in 34/176 (19.3%) and less extensive in 16/176 (9.1%) newborns. Additional anomalies were diagnosed in 24 infants (13.6%), of which 12 (6.8%) were categorized as major. The latter included two submicroscopic chromosome anomalies and two gene mutations. Postnatal additional anomalies occurred more frequently in CLA and CLAP than in CL, and more in bilateral than in unilateral clefts. Major anomalies are still found in infants with a prenatal diagnosis of an isolated oral cleft. The prevalence of additional anomalies seems to be related to the type and bilaterality of the cleft, and this should be considered during prenatal counselling.

Deletion of 1 amino acid in Indian hedgehog leads to brachydactylyA1.

Brachydactyly type A1 is a limb malformation characterized by a uniform shortening of the middle phalanges in all digits. Mutations in the Indian hedgehog (IHH) gene were shown to be the cause of this autosomal dominant disorder. The IHH protein is known to be an important signaling molecule involved in chondrocyte formation. So far, only missense mutations in IHH have been reported to cause BrachydactylyA1. We report here on the first deletion in IHH, p.delE95, causing mild BrachydactylyA1 in a small Dutch family. This brings the total number of different mutations found to cause BDA1 to 7.

[Genetics of craniofacial development]. / Genetica van de ontwikkeling van schedel en aangezicht.

Congenital craniofacial malformations vary widely in both expression and gravity. To understand congenital craniofacial malformations, knowledge of embryonic development is of essential importance. Craniosynostosis has its origin in the failure of suture development between 2 bone centres or in early closure of the suture by bone centre tissue fusion. Hereditary craniosynostosis phenotypes predominantly arise by autosomal dominant inheritance. So far, the majority of mutations have been found in fibroblast growth-factor receptor genes (FGFR-genes). Different phenotypes are not primarily created by disparities of the receptors, but particularly by tissue-specific expressions.

NGS panel analysis in 24 ectopia lentis patients; a clinically relevant test with a high diagnostic yield.

BACKGROUND: Several genetic causes of ectopia lentis (EL), with or without systemic features, are known. The differentiation between syndromic and isolated EL is crucial for further treatment, surveillance and counseling of patients and their relatives. Next generation sequencing (NGS) is a powerful tool enabling the simultaneous, highly-sensitive analysis of multiple target genes. OBJECTIVE: The aim of this study was to evaluate the diagnostic yield of our NGS panel in EL patients. Furthermore, we provide an overview of currently described mutations in ADAMTSL4, the main gene involved in isolated EL. METHODS: A NGS gene panel was analysed in 24 patients with EL. RESULTS: A genetic diagnosis was confirmed in 16 patients (67%). Of these, four (25%) had a heterozygous FBN1 mutation, 12 (75%) were homozygous or compound heterozygous for ADAMTSL4 mutations. The known European ADAMTSL4 founder mutation c.767_786del was most frequently detected. CONCLUSION: The diagnostic yield of our NGS panel was high. Causative mutations were exclusively identified in ADAMTSL4 and FBN1. With this approach the risk of misdiagnosis or delayed diagnosis can be reduced. The value and clinical implications of establishing a genetic diagnosis in patients with EL is corroborated by the description of two patients with an unexpected underlying genetic condition.

Differences in complexity of isolated brachydactyly type C cannot be attributed to locus heterogeneity alone.

Hereditary isolated brachydactyly type C (OMIM 113100) mostly follows an autosomal dominant pattern of inheritance with a marked variability in expression. This phenotype has been mapped to two different loci on chromosomes 12q24 and 20q11.2. The latter locus contains the cartilage-derived morphogenetic protein (CDMP)1 gene, in which a null mutation has been found in patients with malformations restricted to the upper limbs. A more complex brachydactyly type C phenotype has been mapped to chromosome 12q24. Differences in complexity of these phenotypes have been attributed to locus heterogeneity. Clinical subclassification based on the degree of complexity of the phenotype has therefore been suggested. We present patients with a complex brachydactyly type C phenotype in whom there is considerable intra- and interfamilial variability in expression. We show that clinical subclassification based on the complexity of the brachydactyly type C phenotype related to the genetic defect is not feasible. We present evidence that differences in complexity are not only due to locus heterogeneity, but that genetic modifiers and/or environmental factors must also play a role.

Chromosome studies of 500 couples with two or more abortions.

Chromosome studies of 500 couples with recurrent (two or more) spontaneous abortions revealed abnormal karyotypes in 50 partners (10%). There was no apparent relation with the number of abortions. The abnormalities were translocations (44%), mosaicisms (48%), and deletions or inversions (8%). In 20 cases the translocations were reciprocal and mainly maternal. Most mosaicisms involved the maternal X-chromosome. Studies of 78 relatives of the index patients identified another 24 carriers of a balanced translocation. Prenatal diagnosis was performed on 13 carriers of a balanced translocation and 16 carriers of a mosaicism because of their risk of an abnormal fetal karyotype causing serious congenital anomalies. These results illustrate the impact on the families. It is concluded that couples should have chromosome studies after two abortions and that maternal X-chromosomal mosaicism occurs as frequently as a balanced parental translocation.

[From gene to disease; craniosynostosis syndromes due to FGFR2-mutation]. / Van gen naar ziekte; craniosynostosesyndromen door FGFR2-mutaties.

One of the genes involved in craniosynostosis syndromes is the fibroblast growth factor receptor 2 (FGFR2) gene, a tyrosine kinase receptor gene. Upon ligand binding the FGFR2 receptors dimerise, and this is followed by activation of the intracellular tyrosine kinase domains. This initiates a cascade of signals that influence cell division and differentiation. FGFR2 mutations have been found in the Apert, Crouzon and Pfeiffer craniosynostosis syndromes. Most mutations are gain of function mutations, inducing ligand-independent receptor activation or altered ligand binding. With the exception of Apert syndrome, there is no clear genotype-phenotype correlation. Many different mutations have been found in Pfeiffer and Crouzon syndrome, but all of the mutations occur in the same extracellular region of the receptor. Identical mutations have been found in Pfeiffer and Crouzon syndrome. So within one family, both Crouzon and Pfeiffer syndrome may occur. Mutations in other FGFR-genes have also been found in craniosynostosis syndromes.

Phenotypes of craniofrontonasal syndrome in patients with a pathogenic mutation in EFNB1.

Craniofrontonasal syndrome (CFNS) is an X-linked developmental malformation, caused by mutations in the EFNB1 gene, which have only been described since 2004. A genotype-phenotype correlation seems not to be present. As it is of major importance to adequately counsel patients with EFNB1 mutations and their parents, and to improve diagnosis of new patients, more information about the phenotypic features is needed. This study included 23 patients (2 male, 21 female) with confirmed EFNB1 mutations. All patients underwent a thorough physical examination and photographs were taken. If available, radiological images were also consulted. Hypertelorism, longitudinal ridging and/or splitting of nails, a (mild) webbed neck and a clinodactyly of one or more toes were the only consistent features observed in all patients. Frequently observed phenotypic features were bifid tip of the nose (91%), columellar indentation (91%) and low implantation of breasts (90%). In comparison with anthropometric data of facial proportions, patients with CFNS had a significantly different face in multiple respects. An overview of all phenotypic features is shown. Patients with EFNB1 mutations have a clear phenotype. This study will facilitate genetic counseling of parents and patients, and contribute to the diagnostic and screening process of patients with suspected CFNS.

Long-term functional outcome in 167 patients with syndromic craniosynostosis; defining a syndrome-specific risk profile.

OBJECTIVE: Little is known about the long-term prevalence of elevated intracranial pressure (ICP), obstructive sleep apnoea (OSA), level of education, language and motor skills, impaired sight and hearing in craniosynostosis syndromes. The objective of this study was to define the prevalence per syndrome of elevated ICP, OSA, impaired sight and impaired hearing. METHODS: A retrospective study was undertaken on 167 consecutive patients diagnosed with Apert, Crouzon, Pfeiffer, Muenke or Saethre-Chotzen syndrome, aged 1-25 years and treated between 1983 and 2008. The mean age at time of referral and review was 1 years and 2 months and 10 years and 3 months, respectively. RESULTS: Patients with Apert and Crouzon/Pfeiffer syndromes had the highest prevalence of elevated ICP (33% and 53%, respectively) and OSA (31% and 27%, respectively), while Saethre-Chotzen syndrome was also associated with a fair risk for elevated ICP (21%). The prevalence of impaired sight (61%) and hearing (56%) was high in all syndromes. CONCLUSION: Based on these data, a syndrome-specific risk profile with suggestions for screening and treatment is presented.

[Prenatally detected orofacial cleft]. / Prenataal vastgestelde orofaciale schisis.

An increasing number of pregnancies are presumed being terminated following prenatal detection of orofacial cleft during structural ultrasound.After examining the data and literature on this topic it is concluded that the reported cases are merely incidents. For the interpretation of prenatal detection rates a distinction should be made between isolated orofacial cleft and the frequently occurring associated form of orofacial cleft which is usually characterized by other, often major structural or chromosome anomalies. The ultrasound detection rate of the isolated form is low and varies in the literature between 18 and 56%. Together with all Dutch centres of prenatal medicine a care plan was adopted for the management of prenatally detected orofacial cleft including diagnosis (detailed ultrasound examination and karyotyping), medical support (genetic consultations, plastic surgery and psychosocial counselling) and treatment (obstetric and neonatal management). In the presence of associated major congenital anomalies termination of pregnancy may be considered before the 24th week of pregnancy.

Somatic cell hybridisation studies showing different gene mutations in Niemann-Pick variants.

Cultured skin fibroblasts from patients with different clinical types of Niemann-Pick disease were hybridized and sphingomyelinase activities were measured in the heterokaryon cell population. Both the natural substrate (3H-choline) sphingomyelin and the chromogenic analogue hexadecanoylamino-4-nitrophenylphosphorylcholine were used in the complementation analysis. In fusions between cells from type C Niemann-Pick disease with those from type A or B a clear restoration of sphingomyelinase activity occurred, whereas no complementation was found in other fusion combinations. The results indicate that at least two different genes are involved in the mutations leading to the different Niemann-Pick variants.

Interstitial del(13)(q21.3q31) associated with psychomotor retardation, eczema, and absent suck and swallowing reflex.

A patient with a deletion (13)(q21.3q31) showed only eczema and absent suck and swallowing reflex, in contrast to other well documented cases with a similar deletion. Apparently there is wide clinical variability in patients with deletions in this area.

Prenatal diagnosis of type A1 brachydactyly.

Brachydactyly can occur as an isolated malformation or as part of numerous syndromes. Prenatal assessment of brachydactyly may be especially helpful in multiple anomaly syndromes associated with hand and/or finger anomalies. In isolated type A1 brachydactyly, which is an autosomal dominant disorder, all middle phalanges of the fingers and toes are affected. We present a fetus with type A1 brachydactyly inherited from the mother and grandmother.

The Aarskog syndrome in a large family, suggestive for autosomal dominant inheritance.

A large family in which the Aarskog syndrome is transmitted in three generations was studied. In affected males, a large variability of expression was observed, while females show minor signs only. However it is sometimes possible to identify individual females as carriers. The observation of male to male transmission and the absence of symptoms in some daughters of affected male persons suggest a sex-influenced autosomal inheritance in this family. This may suggest heterogeneity in the Aarskog syndrome, since in most families described an X-linked recessive mode of inheritance was indicated.

Deletion of the TWIST gene in a large five-generation family.

In this article, we describe a large five-generation family with characteristics of the Saethre-Chotzen syndrome as well as of the blepharophimosis ptosis epicanthus inversus syndrome. Segregating with their phenotype is a deletion of the chromosome 7p21 TWIST gene locus. The TWIST gene indeed is involved in Saethre-Chotzen syndrome, a craniosynostosis syndrome further characterized by specific facial and limb abnormalities. However, only two members of our family exhibited craniosynostosis. This report demonstrates that the genetics of craniofacial anomalies are less straightforward than they sometimes appear to be. Not only craniosynostosis, but also subtle facial deformities could be indicative of an abnormality of the TWIST gene. In conclusion, the clinical spectrum of genetic abnormalities of the TWIST gene is highly variable. We therefore recommend that genetic analysis of the TWIST gene locus, including fluorescence in situ hybridization, should be considered in familial cases of facial and eyelid abnormalities without the presence of craniosynostosis.