A B3GALT6 variant in patient originally described as Al-Gazali syndrome and implicating the endoplasmic reticulum quality control in the mechanism of some ß3GalT6-pathy mutations.

Al-Gazali syndrome encompasses several clinical features including prenatal growth retardation, large joints contractures with camptodactyly, bilateral talipes equinovarus, small mouth, anterior segment anomalies of the eyes, and early lethality. Recently, a baby with features very similar to Al-Gazali syndrome was found to have compound heterozygous variants in B3GALT6. This gene encodes Beta-1,3-galactosyltransferase 6 (ß3GalT6), an essential component of the glycosaminoglycan synthesis pathway. Pathogenic variants in B3GALT6 have also been shown to cause Ehlers-Danlos syndrome spondylodysplastic type (spEDS-B3GALT6) and spondyloepimetaphyseal dysplasia with joint laxity type I (SEMD-JL1). In 2017, a new international classification of EDS included these 2 conditions together with the child reported to have features similar to Al-Gazali syndrome under spondylodysplastic EDS (spEDS). We report a disease-causing variant c.618C > G, p.(Cys206Trp) in 1 patient originally described as Al-Gazali syndrome and reported in 1999. We evaluated the involvement of the endoplasmic reticulum-associated protein degradation, in the pathogenesis of 13 B3GALT6 variants. Retention in endoplasmic reticulum was evident in 6 of them while the c.618C > G, p.(Cys206Trp) and the other 6 variants trafficked normally. Our findings confirm the involvement of B3GALT6 in the pathogenesis of Al-Gazali syndrome and suggest that Al-Gazali syndrome represents the severe end of the spectrum of the phenotypes caused by pathogenic variants in this gene.

Expanding the clinical and genetic spectra of NKX6-2-related disorder.

Hypomyelinating leukodystrophies (HLDs) affect the white matter of the central nervous system and manifest as neurological disorders. They are genetically heterogeneous. Very recently, biallelic variants in NKX6-2 have been suggested to cause a novel form of autosomal recessive HLD. Using whole-exome or whole-genome sequencing, we identified the previously reported c.196delC and c.487C>G variants in NKX6-2 in 3 and 2 unrelated index cases, respectively; the novel c.608G>A variant was identified in a sixth patient. All variants were homozygous in affected family members only. Our patients share a primary diagnosis of psychomotor delay, and they show spastic quadriparesis, nystagmus and hypotonia. Seizures and dysmorphic features (observed in 2 families each) represent an addition to the phenotype, while developmental regression (observed in 3 families) appears to be a notable and previously underestimated clinical feature. Our findings extend the clinical and mutational spectra associated with this novel form of HLD. Comparative analysis of our 10 patients and the 15 reported previously did, however, not reveal clear evidence for a genotype-phenotype correlation.

Chondrodysplasia with multiple dislocations: comprehensive study of a series of 30 cases.

The group of chondrodysplasia with multiple dislocations includes several entities, characterized by short stature, dislocation of large joints, hand and/or vertebral anomalies. Other features, such as epiphyseal or metaphyseal changes, cleft palate, intellectual disability are also often part of the phenotype. In addition, several conditions with overlapping features are related to this group and broaden the spectrum. The majority of these disorders have been linked to pathogenic variants in genes encoding proteins implicated in the synthesis or sulfation of proteoglycans (PG). In a series of 30 patients with multiple dislocations, we have performed exome sequencing and subsequent targeted analysis of 15 genes, implicated in chondrodysplasia with multiple dislocations, and related conditions. We have identified causative pathogenic variants in 60% of patients (18/30); when a clinical diagnosis was suspected, this was molecularly confirmed in 53% of cases. Forty percent of patients remain without molecular etiology. Pathogenic variants in genes implicated in PG synthesis are of major importance in chondrodysplasia with multiple dislocations and related conditions. The combination of hand features, growth failure severity, radiological aspects of long bones and of vertebrae allowed discrimination among the different conditions. We propose key diagnostic clues to the clinician.

Fibrochondrogenesis: prenatal diagnosis and outcome.

We studied 20 cases with fibrochondrogenesis (FCG) diagnosed prenatally. Four cases were diagnosed at our fetal unit, and 16 cases were identified through a review of literature (in English). The prenatal diagnosis of FCG was made in 4/20 (20%). Six (30%) patients opted for termination of pregnancy (TOP). A total of 13 cases delivered at term. Four (30.8%) had a caesarean section. Four neonates (30.7%) were stillborn and seven (53.8%) neonates died within 3 months. Two infants survived beyond 3 years of age, but both had severe global developmental delay. A molecular study of the surviving children revealed two null homozygous mutations in COL11A1 [c.4084C > T (p.R1362X) and c.3708 + c.437T > G]. We concluded that the prenatal diagnosis of fibrochondrogenesis is feasible. Fibrochondrogenesis is usually a fatal disease and survivors suffer from severe physical and neurological impairment.

Evaluation of Clinical Manifestations in Patients with Severe Lymphedema with and without CCBE1 Mutations.

The lymphedema-lymphangiectasia-intellectual disability (Hennekam) syndrome (HS) is characterised by a widespread congenital lymph vessel dysplasia manifesting as congenital lymphedema of the limbs and intestinal lymphangiectasia, accompanied by unusual facial morphology, variable intellectual disabilities and infrequently malformations. The syndrome is heterogeneous as mutations in the gene CCBE1 have been found responsible for the syndrome in only a subset of patients. We investigated whether it would be possible to predict the presence of a CCBE1 mutation based on phenotype by collecting clinical data of patients diagnosed with HS, with or without a CCBE1 mutation. We report here the results of 13 CCBE1 positive patients, 16 CCBE1 negative patients, who were clinically found to have classical HS, and 8 patients in whom the diagnosis was considered possible, but not certain, and in whom no CCBE1 mutation was identified. We found no statistically significant phenotypic differences between the 2 groups with the clinical HS phenotype, although the degree of lymphatic dysplasia tended to be more pronounced in the mutation positive group. We also screened 158 patients with less widespread and less pronounced forms of lymphatic dysplasia for CCBE1 mutations, and no mutation was detected in this group. Our results suggest that (1) CCBE1 mutations are present only in patients with a likely clinical diagnosis of HS, and not in patients with less marked forms of lymphatic dysplasia, and (2) that there are no major phenotypic differences between HS patients with or without CCBE1 mutations.

A Novel Aberrant Splice Site Mutation in RAB23 Leads to an Eight Nucleotide Deletion in the mRNA and Is Responsible for Carpenter Syndrome in a Consanguineous Emirati Family.

Carpenter syndrome is caused by mutations in the RAB23 gene that encodes a small GTPase of the Rab subfamily of proteins. Rab proteins are known to be involved in the regulation of cellular trafficking and signal transduction. Currently, only few mutations in RAB23 have been reported in patients with Carpenter syndrome. In this paper, we report the clinical features, molecular and functional analysis of 2 children from an Emirati consanguineous family with this syndrome. The affected children exhibit the typical features including craniosynostosis, typical facial appearance, polysyndactyly, and obesity. Molecular analysis of the RAB23 gene revealed a homozygous mutation affecting the first nucleotide of the acceptor splice site of exon 5 (c.482-1G>A). This mutation affects the authentic mRNA splicing and activates a cryptic acceptor site within exon 5. Thus, the erroneous splicing results in an eight nucleotide deletion, followed by a frameshift and premature termination codon at position 161 (p.V161fsX3). Due to the loss of the C-terminally prenylatable cysteine residue, the truncated protein will probably fail to associate with the target cellular membranes due to the absence of the necessary lipid modification. The p.V161fsX3 extends the spectrum of RAB23 mutations and points to the crucial role of prenylation in the pathogenesis of Carpenter syndrome within this family.

Stüve-Wiedemann syndrome and related bent bone dysplasias.

Stüve-Wiedemann syndrome (SWS) is a severe congenital skeletal dysplasia associated with life threatening dysautonomic manifestations. Newborns affected with this condition exhibit distinctive shortening and bowing of the long bones with reduced bone volume. The majority of affected newborns die early due to neuromuscular complications namely hyperthermia, apnea, and swallowing difficulties. In this review, we provide an overall picture on the clinical, including long-term management, molecular and cellular aspects of SWS and discuss briefly other related bent bone dysplasias.

Clinical and molecular analysis of UAE fibrochondrogenesis patients expands the phenotype and reveals two COL11A1 homozygous null mutations.

Fibrochondrogenesis is documented to be a neonatally lethal rare recessively inherited disorder characterized by short-limbed skeletal dysplasia. Here we report two patients from two unrelated consanguineous Emirati families who have unexpectedly survived till the ages of 3 and 6 years. These patients show additional symptoms which include developmental delay, profound sensory-neural deafness, severe myopia and progressive severe skeletal abnormalities. Linkage of fibrochondrogenesis in the Emirati families to chromosome 1 has been established using homozygosity mapping confirming recent findings by Tompson et al. in 2010. Screening of the COL11A1 gene revealed two null homozygous mutations [c.4084C>T (p.R1362X) and c.3708+437T>G] in the aforementioned two families. The c.4084C>T mutation is predicted to introduce a stop codon at position Arg1362, whereas the c.3708+437T>G mutation causes the activation of an intronic pseudoexon between exons 48 and 49. This resulted in the insertion of 50 nucleotides into the mRNA. The carriers of these mutations display ocular defects with normal hearing. In conclusion, our data shall improve the overall understanding of fibrochondrogenesis especially in surviving homozygous patients and, at least partly, explain the phenotypic variability associated with COL11A1 gene mutations.

Stuve-Wiedemann syndrome: a skeletal dysplasia characterized by bowed long bones.

OBJECTIVE: To describe the prenatal sonographic features of Stuve-Wiedemann syndrome (SWS). METHODS: A retrospective review of all cases of confirmed SWS during an 8-year period was conducted. Clinical and historical data and outcome of the pregnancies were noted. Fetal biometry, skeletal survey, amniotic fluid volume and associated anomalies were recorded. A sonographic algorithm was proposed to distinguish SWS from other bent bone disorders. RESULTS: In total, there were 10 cases, six of which were diagnosed prenatally. The main prenatal features of SWS were mild-to-moderate micromelia and bowing of the lower limb bones, affecting the tibia more than the femur. There was relative sparing of fibula and upper limb bones, with normal scapulae and clavicles. Camptodactyly was the main associated anomaly. All fetuses developed growth restriction in the late second trimester with oligohydramnios in half of the cases. These features could appear late in pregnancy. Although the thoracic dimensions were normal in the majority of fetuses, respiratory insufficiency, as a result of myotonia, was a leading cause for mortality. CONCLUSIONS: It is possible to diagnose SWS prenatally. SWS is associated with high mortality during the first year of life, and those who survive have high morbidity.

Distinguishing 3 classes of corpus callosal abnormalities in consanguineous families.

OBJECTIVE: We sought to create a classification system for pediatric corpus callosal abnormalities (CCA) based upon midline sagittal brain MRI. We used the term CCA for patients with structural variants of the corpus callosum, excluding patients with interhemispheric cyst variant or pure dysplasia without hypoplasia. Currently, no system exists for nonsyndromic forms of CCA, and attempts to create such a system have been hampered by highly variable morphology in patients with sporadic CCA. We reasoned that any useful strategy should classify affected family members within the same type, and that phenotypic variability should be minimized in patients with recessive disease. METHODS: We focused recruitment toward multiplex consanguineous families, ascertained 30 patients from 19 consanguineous families, and analyzed clinical features together with brain imaging. RESULTS: We identified 3 major CCA classes, including hypoplasia, hypoplasia with dysplasia, and complete agenesis. Affected individuals within a given multiplex family usually displayed the same variant of the class of abnormality and they always displayed the same class of abnormality within each family, or they displayed complete agenesis. The system was validated among a second cohort of 10 sporadic patients with CCA. CONCLUSIONS: The data suggest that complete agenesis may be a common end-phenotype, and implicate multiple overlapping pathways in the etiology of CCA.

A new autosomal recessive syndrome of ocular colobomas, ichthyosis, brain malformations and endocrine abnormalities in an inbred Emirati family.

We report on an inbred Emirati family of Baluchi origin with ocular colobomas, ichthyosis, and endocrine abnormalities associated with midline brain malformations and mental retardation. All affected children had ocular colobomas, developmental delay and midline brain malformations. Hypoplastic pituitary gland was present in all three investigated children. Ichthyosiform dermatitis appeared in infancy in all surviving children. Other variable features include congenital heart defects, hypertrichosis and dark skin involving the dorsum of hands and feet associated with mild degree of palmo-plantar keratoderma. Some of the features in this family overlap the CHIME (Coloboma of the eye, Heart defect, Ichthyosiform dermatosis, Mental retardation, and Ear defect) syndrome. However, several features described in CHIME syndrome were not present in these children. These include deafness, seizures, oligodontia, and hair abnormalities. Some of the features in these children also overlap with septo-optic dysplasia (SOD) but optic nerve hypoplasia, mandatory for the diagnosis of SOD, was present in one child only. We suggest that these children have a new autosomal recessive syndrome of ocular colobomas and ichthyosis.

Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development.

The generation and homeostasis of bone tissue throughout development and maturity is controlled by the carefully balanced processes of bone formation and resorption. Disruption of this balance can give rise to a broad range of skeletal pathologies. Lethal osteosclerotic bone dysplasia (or, Raine syndrome) is an autosomal recessive disorder characterized by generalized osteosclerosis with periosteal bone formation and a distinctive facial phenotype. Affected individuals survive only days or weeks. We have identified and defined a chromosome 7 uniparental isodisomy and a 7p telomeric microdeletion in an affected subject. The extent of the deleted region at the 7p telomere was established by genotyping microsatellite markers across the telomeric region. The region is delimited by marker D7S2563 and contains five transcriptional units. Sequence analysis of FAM20C, located within the deleted region, in six additional affected subjects revealed four homozygous mutations and two compound heterozygotes. The identified mutations include four nonsynonymous base changes, all affecting evolutionarily conserved residues, and four splice-site changes that are predicted to have a detrimental effect on splicing. FAM20C is a member of the FAM20 family of secreted proteins, and its mouse orthologue (DMP4) has demonstrated calcium-binding properties; we also show by in situ hybridization its expression profile in mineralizing tissues during development. This study defines the causative role of FAM20C in this lethal osteosclerotic disorder and its crucial role in normal bone development.

Radiological manifestations of the skeleton, lungs and brain in Stueve-Wiedemann syndrome.

A total of 25 patients with the rare skeletal dysplasia Stueve-Wiedemann syndrome (SWS) have been evaluated during the last 11 years. Of all patients with clinical suspicion of SWS, skeletal and chest radiographs were obtained for classification of the underlying skeletal dysplasia. In one case, CT was carried out for the first time for further investigation of the midface hypoplasia. Typical conventional radiological findings and CT features were analysed and compared with published data. Early diagnosis of SWS was made by correlating radiological and clinical findings. Follow-up radiological examinations of the skeleton and of the chest were carried out in six children surviving infancy for evaluation of progression. Clinically, they suffered from progressive orthopaedic problems, recurrent aspiration pneumonia and recurrent episodes of hyperthermia, as well as cutaneous infections. Radiologically progressive bowing of the long tubular bones and progressive metaphyseal decalcification were present on follow-up skeletal radiographs. Skeletal abnormalities in SWS are so characteristic that an early post-partum diagnosis can be made by correlation of typical clinical and radiological findings. Few cases survive infancy. First, these patients face progressive orthopaedic problems and respiratory infections.

Mutations in cytokine receptor-like factor 1 (CRLF1) account for both Crisponi and cold-induced sweating syndromes.

Crisponi syndrome is a rare autosomal recessive disorder characterized by congenital muscular contractions of facial muscles, with trismus in response to stimuli, dysmorphic features, bilateral camptodactyly, major feeding and respiratory difficulties, and access of hyperthermia leading to death in the first months of life. The overlap with Stuve-Wiedemann syndrome (SWS) is striking, but the two conditions differ in that congenital lower limb bowing is absent in Crisponi syndrome, whereas it is a cardinal feature of SWS. We report here the exclusion of the leukemia inhibitory factor receptor gene in Crisponi syndrome and the identification of homozygote or compound heterozygote cytokine receptor-like factor 1 (CRLF1) mutations in four children from three unrelated families. The four mutations were located in the immunoglobulin-like and type III fibronectin domains, and three of them predicted premature termination of translation. Using real-time quantitative polymerase chain reaction, we found a significant decrease in CRLF1 mRNA expression in patient fibroblasts, which is suggestive of a mutation-mediated decay of the abnormal transcript. CRLF1 forms a heterodimer complex with cardiotrophin-like cytokine factor 1, and this heterodimer competes with ciliary neurotrophic factor for binding to the ciliary neurotrophic factor receptor (CNTFR) complex. The identification of CRLF1 mutations in Crisponi syndrome supports the key role of the CNTFR pathway in the function of the autonomic nervous system.

Mutations in WNT7A cause a range of limb malformations, including Fuhrmann syndrome and Al-Awadi/Raas-Rothschild/Schinzel phocomelia syndrome.

Fuhrmann syndrome and the Al-Awadi/Raas-Rothschild/Schinzel phocomelia syndrome are considered to be distinct limb-malformation disorders characterized by various degrees of limb aplasia/hypoplasia and joint dysplasia in humans. In families with these syndromes, we found homozygous missense mutations in the dorsoventral-patterning gene WNT7A and confirmed their functional significance in retroviral-mediated transfection of chicken mesenchyme cell cultures and developing limbs. The results suggest that a partial loss of WNT7A function causes Fuhrmann syndrome (and a phenotype similar to mouse Wnt7a knockout), whereas the more-severe limb truncation phenotypes observed in Al-Awadi/Raas-Rothschild/Schinzel phocomelia syndrome result from null mutations (and cause a phenotype similar to mouse Shh knockout). These findings illustrate the specific and conserved importance of WNT7A in multiple aspects of vertebrate limb development.

A novel locus for hereditary spastic paraplegia with thin corpus callosum and epilepsy.

BACKGROUND: Hereditary spastic paraplegia (HSP) are classified clinically as pure when progressive spasticity occurs in isolation or complicated when other neurologic abnormalities are present. At least 22 genetic loci have been linked to HSP, 8 of which are autosomal recessive (ARHSP). HSP complicated with the presence of thin corpus callosum (HSP-TCC) is a common subtype of HSP. One genetic locus has been identified on chromosome 15q13-q15 (SPG11) for HSP-TCC, but some HSP-TCC families have not been linked to this locus. METHODS: The authors characterized two families clinically and radiologically and performed a genome-wide scan and linkage analysis. RESULTS: The two families had complicated ARHSP. The affected individuals in Family A had thin corpus callosum and mental retardation, whereas in Family B two of three affected individuals had epilepsy. In both families linkage analysis identified a locus on chromosome 8 between markers D8S1820 and D8S532 with the highest combined lod score of 7.077 at marker D8S505. This 9 cM interval located on 8p12-p11.21 represents a new locus for ARHSP-TCC. Neuregulin and KIF13B genes, located within this interval, are interesting functional candidate genes for this HSP form. CONCLUSION: Two consanguineous families with complicated autosomal recessive hereditary spastic paraplegia were clinically characterized and genetically mapped to a new locus on 8p12-p11.21.

United Arab Emirates: communities and community genetics.

The UAE society is cosmopolitan, but the indigenous inhabitants are traditional with puritanical values despite their exposure to other vastly different cultures and habits. Marriages between consanguineous couples are still the norm rather than the exception. As a result, there is a high frequency of genetic disorders, particularly autosomal recessive types. Despite the high frequency of genetic disorders like haemoglobinopathies and others characteristically found in this population, genetic services are inadequate. Screening for certain disorders like thalassaemia are not applied on a wide scale. Abortion is illegal, and therefore, prenatal diagnosis or preconception tests are not done. With the absence of a good national database, deficiency of genetic services and absence of preventative alternatives for carrier couples, genetic counsellors find it difficult to advice pragmatic solutions to issues relating to genetic diseases. This paper reviews common genetic problems in the UAE with special emphasis on available genetic services and support to families with children with inherited disorders. Existing barriers to the improvement of clinical services by prenatal counselling are also discussed.

Genetic contribution to high neonatally lethal malformation rate in the United Arab Emirates.

OBJECTIVES: We examined the contribution of genetic disorders to congenital anomalies (CA) causing neonatal deaths in the Al Ain Medical District (AMD) in the United Arab Emirates (UAE) because of the high consanguineous marriage rate in the community. METHODS: Charts of all neonatal deaths in the three perinatal units, which accounted for 99% of all births in AMD (1992-2000), were studied. Data regarding pregnancy, a family history including the level of parental consanguinity, the results of genetic evaluations and neonatal outcomes were recorded as part of an ongoing malformation surveillance system. Causes of death were based on clinical, laboratory and imaging findings. RESULTS: Of the 508 neonates who died, 212 (42%) had CA, which were the leading cause of death. Forty-four percent of the CA were due to definite genetic disorders and 75% of these were single gene defects. Multisystem malformations were the commonest congenital malformations. Parental consanguinity was associated with a 2-fold increased risk of non-chromosomal multisystem malformations. CONCLUSIONS: Lethal malformations were the leading cause of neonatal deaths, and parental consanguinity was associated with an increased risk of autosomal recessive disorders. The results underscore the importance of genetic screening and counseling in strategies for further significant reductions in the neonatal mortality rate in the UAE.