Expansion and further delineation of the SETD5 phenotype leading to global developmental delay, variable dysmorphic features, and reduced penetrance.

Diagnostic exome sequencing (DES) has aided delineation of the phenotypic spectrum of rare genetic etiologies of intellectual disability (ID). A SET domain containing 5 gene (SETD5) phenotype of ID and dysmorphic features has been previously described in relation to patients with 3p25.3 deletions and in a few individuals with de novo sequence alterations. Herein, we present additional patients with pathogenic SETD5 sequence alterations. The majority of patients in this cohort and previously reported have developmental delay, behavioral/psychiatric issues, and variable hand and skeletal abnormalities. We also present an apparently unaffected carrier mother of an affected individual and a carrier mother with normal intelligence and affected twin sons. We suggest that the phenotype of SETD5 is more complex and variable than previously presented. Therefore, many features and presentations need to be considered when evaluating a patient for SETD5 alterations through DES.

Attenuated phenotype of Costello syndrome and early death in a patient with an HRAS mutation (c.179G>T; p.Gly60Val) affecting signalling dynamics.

Costello syndrome (CS) is caused by heterozygous germline HRAS mutations. Most patients share the HRAS mutation c.34G>A (p.Gly12Ser) associated with the typical, relatively homogeneous phenotype. Rarer mutations occurred in individuals with an attenuated phenotype. Although many disease-associated HRAS alterations trigger constitutive activation of HRAS-dependent signalling pathways, additional pathological consequences exist. An infant with failure-to-thrive and hypertrophic cardiomyopathy had a novel de novo HRAS mutation (c.179G>T; p.Gly60Val). He showed subtle dysmorphic findings consistent with attenuated CS and died from presumed cardiac cause. Functional studies revealed that amino acid change p.Gly60Val impairs HRAS binding to effectors PIK3CA, phospholipase C1, and RAL guanine nucleotide dissociation stimulator. In contrast, interaction with effector rapidly accelerated fibrosarcoma (RAF) and regulator NF1 GTPase-activating protein was enhanced. Importantly, expression of HRAS p.Gly60Val in HEK293 cells reduced growth factor sensitivity leading to damped RAF-MAPK and phosphoinositide 3-kinases-AKT signalling response. Our data support the idea that a variable range of dysregulated HRAS-dependent signalling dynamics, rather than static activation of HRAS-dependent signal flow, may underlie the phenotypic variability in CS.

Constitutional LZTR1 mutation presenting with a unilateral vestibular schwannoma in a teenager.

Schwannomatosis is a rare neurofibromatosis clinically diagnosed by age-dependent criteria, with bilateral vestibular schwannoma and/or a constitutional NF2 mutation representing exclusion criteria. Following SMARCB1 germline mutations, constitutional mutations in LZTR1 were discovered. We report on the molecular investigation in a patient presenting at 14 years with a unilateral vestibular schwannoma, ultimately causing blindness and unilateral hearing loss, in the absence of other schwannomas or a positive family history. In DNA derived from frozen tumor tissue, a comprehensive NF2, SMARCB1 and LZTR1 analysis showed an NF2 truncating mutation c.1006_1021delins16; an LZTR1 mutation c.791+1G>A; and a partial 22q deletion including NF2, SMARCB1 and LZTR1. Sequence analysis on peripheral blood derived DNA showed the LZTR1 mutation to be constitutional, but the NF2 mutation and partial 22q deletion were not found, indicating them to be somatic events. RNA-based targeted analysis confirmed missplicing of LZTR1 intron 8, predicted to result in a premature stop codon. This LZTR1 mutation was paternally inherited. While isolated vestibular schwannoma or NF2 may be considered in a young individual with a unilateral vestibular schwannoma, this report suggests that LZTR1 -related schwannomatosis be added to this differential diagnosis.

Microcephaly, intractable seizures and developmental delay caused by biallelic variants in TBCD: further delineation of a new chaperone-mediated tubulinopathy.

Microtubule dynamics play a crucial role in neuronal development and function, and several neurodevelopmental disorders have been linked to mutations in genes encoding tubulins and functionally related proteins. Most recently, variants in the tubulin cofactor D (TBCD) gene, which encodes one of the five co-chaperones required for assembly and disassembly of α/ß-tubulin heterodimer, were reported to underlie a recessive neurodevelopmental/neurodegenerative disorder. We report on five patients from three unrelated families, who presented with microcephaly, intellectual disability, intractable seizures, optic nerve pallor/atrophy, and cortical atrophy with delayed myelination and thinned corpus callosum on brain imaging. Exome sequencing allowed the identification of biallelic variants in TBCD segregating with the disease in the three families. TBCD protein level was significantly reduced in cultured fibroblasts from one patient, supporting defective TBCD function as the event underlying the disorder. Such reduced expression was associated with accelerated microtubule re-polymerization. Morpholino-mediated TBCD knockdown in zebrafish recapitulated several key pathological features of the human disease, and TBCD overexpression in the same model confirmed previous studies documenting an obligate dependency on proper TBCD levels during development. Our findings confirm the link between inactivating TBCD variants and this newly described chaperone-associated tubulinopathy, and provide insights into the phenotype of this disorder.

Mutations in RIT1 cause Noonan syndrome - additional functional evidence and expanding the clinical phenotype.

RASopathies are a clinically heterogeneous group of conditions caused by mutations in 1 of 16 proteins in the RAS-mitogen activated protein kinase (RAS-MAPK) pathway. Recently, mutations in RIT1 were identified as a novel cause for Noonan syndrome. Here we provide additional functional evidence for a causal role of RIT1 mutations and expand the associated phenotypic spectrum. We identified two de novo missense variants p.Met90Ile and p.Ala57Gly. Both variants resulted in increased MEK-ERK signaling compared to wild-type, underscoring gain-of-function as the primary functional mechanism. Introduction of p.Met90Ile and p.Ala57Gly into zebrafish embryos reproduced not only aspects of the human phenotype but also revealed abnormalities of eye development, emphasizing the importance of RIT1 for spatial and temporal organization of the growing organism. In addition, we observed severe lymphedema of the lower extremity and genitalia in one patient. We provide additional evidence for a causal relationship between pathogenic mutations in RIT1, increased RAS-MAPK/MEK-ERK signaling and the clinical phenotype. The mutant RIT1 protein may possess reduced GTPase activity or a diminished ability to interact with cellular GTPase activating proteins; however the precise mechanism remains unknown. The phenotypic spectrum is likely to expand and includes lymphedema of the lower extremities in addition to nuchal hygroma.

Mutations in TGIF cause holoprosencephaly and link NODAL signalling to human neural axis determination.

Holoprosencephaly (HPE) is the most common structural defect of the developing forebrain in humans (1 in 250 conceptuses, 1 in 16,000 live-born infants). HPE is aetiologically heterogeneous, with both environmental and genetic causes. So far, three human HPE genes are known: SHH at chromosome region 7q36 (ref. 6); ZIC2 at 13q32 (ref. 7); and SIX3 at 2p21 (ref. 8). In animal models, genes in the Nodal signalling pathway, such as those mutated in the zebrafish mutants cyclops (refs 9,10), squint (ref. 11) and one-eyed pinhead (oep; ref. 12), cause HPE. Mice heterozygous for null alleles of both Nodal and Smad2 have cyclopia. Here we describe the involvement of the TG-interacting factor (TGIF), a homeodomain protein, in human HPE. We mapped TGIF to the HPE minimal critical region in 18p11.3. Heterozygous mutations in individuals with HPE affect the transcriptional repression domain of TGIF, the DNA-binding domain or the domain that interacts with SMAD2. (The latter is an effector in the signalling pathway of the neural axis developmental factor NODAL, a member of the transforming growth factor-beta (TGF-beta) family.) Several of these mutations cause a loss of TGIF function. Thus, TGIF links the NODAL signalling pathway to the bifurcation of the human forebrain and the establishment of ventral midline structures.

Apparently new syndrome of congenital cataracts, sensorineural deafness, Down syndrome-like facial appearance, short stature, and mental retardation.

We describe a previously unrecognized syndrome in two unrelated patients with congenital cataracts, sensorineural deafness, distinctive facial appearance, skeletal changes, postnatal short stature, and mental retardation.

Extending the spectrum of distal arthrogryposis.

We describe a mother and son with multiple, non-progressive, congenital contractures, camptodactyly and absent flexion creases, expressionless face, blepharophimosis, microstomia, and short stature. Although these cases share similarities with the autosomal-recessive Schwartz-Jampel and Marden-Walker syndromes, they have a different mode of inheritance and lack myotonia, one of the most characteristic findings of the Schwartz-Jampel syndrome. Our cases most closely resemble those previously reported as distal arthrogryposis type IIb, although in our patients the proximal joints are severely affected and extraocular involvement is absent. Hearing loss is present in one and cleft palate in the other of our patients; these findings were previously described in arthrogryposis syndromes other than type IIb. We suggest extending the spectrum of distal arthrogryposis to include these manifestations, since there appears to be significantly overlap between the different syndromes.

Nasal dimple as part of the 22q11.2 deletion syndrome.

The phenotype of the 22q11.2 microdeletion syndrome is quite variable. We describe 2 patients with a 22q11.2 deletion and a dimpled nasal tip, which, we suggest can be the extreme of the broad or bulbous nose commonly found in the 22q11.2 deletion syndrome, and should not be confused with the more severe nasal abnormalities seen in frontonasal dysplasia.

Diaphragmatic hernia-exomphalos-hypertelorism syndrome: a new case and further evidence of autosomal recessive inheritance.

We describe a male patient with wide anterior fontanel and metopic suture, hypertelorism, down slanting palpebral fissures, bilateral iris coloboma, omphalocele, and bilateral absence of the diaphragm with herniation of abdominal organs causing pulmonary hypoplasia and death. Autopsy also showed intestinal malrotation. All findings in this case are consistent with those described as a newly recognized syndrome by Donnai and Barrow [1993]. Since the parents are first cousins, this case provides further evidence for the previously postulated autosomal recessive inheritance pattern. Follow-up on the patients and families reported by Donnai and Barrow [1993] also supports autosomal recessive inheritance.

TWIST gene mutation in a patient with radial aplasia and craniosynostosis: further evidence for heterogeneity of Baller-Gerold syndrome.

The term Baller-Gerold syndrome was coined by Cohen [1979: Birth Defects 15(5B): 13-63] to designate the phenotype of craniosynostosis and radial aplasia. It is thought to be a rare autosomal recessive condition, which, in some patients, presents with additional abnormalities, such as polymicrogyria, mental retardation or anal atresia. A phenotypic overlap of Baller-Gerold and Roberts-SC phocomelia syndrome was noted when a patient with bicoronal synostosis and bilateral radial hypoplasia was found to have premature centromere separation, a finding characteristic of Roberts syndrome [Huson et al.,1990: J Med Genet 27:371-375]. Other cases of presumed Baller-Gerold syndrome were rediagnosed as Fanconi pancytopenia, Rothmund-Thomson syndrome or VACTERL association. These reports led to a narrowed redefinition of Baller-Gerold syndrome based on the exclusion of cytogenetic and hematopoetic abnormalities and the absence of additional malformations in patients with craniosynostosis and preaxial upper limb abnormalities. Here we report on a patient with unilateral radial aplasia and bicoronal synostosis without additional malformations and without chromosome breakage, who fits this narrow definition of Baller-Gerold syndrome. We identified a novel TWIST gene mutation in this patient, a Glu181Stop mutation predicting a premature termination of the protein carboxy-terminal to the helix 2 domain. This report provides further evidence that Baller-Gerold is of heterogeneous cause, and a thorough evaluation is indicated to identify a possibly more specific diagnosis, including Saethre-Chotzen syndrome. This differential diagnosis is of particular importance, as it is an autosomal dominant trait. Therefore, the recurrence risk for parents of an affected child can be 50% if one parent carries the mutation, as opposed to the 25% recurrence risk for autosomal recessive inheritance. Offspring of the affected patient also have a 50% risk to inherit the mutation, while the risk to bear an affected offspring for an autosomal recessive trait is very low.

Aphallia as part of urorectal septum malformation sequence in an infant of a diabetic mother.

A male patient with aphallia, anal stenosis, tetralogy of Fallot, multiple vertebral anomalies including sacral agenesis and central nervous system (CNS) malformations was born after a pregnancy complicated by poorly controlled maternal diabetes. Aphallia is an extremely rare abnormality and can be part of the urorectal septum malformation sequence (URSMS). While aphallia has not been reported in infants of diabetic mothers, urogenital malformations are known to occur with increased frequency. Two female products of pregnancies complicated by diabetes presented with multiple malformations including anal atresia and recto-vaginal fistula consistent with the diagnosis of URSMS. The three patients share CNS, cardiac, and vertebral anomalies, abnormalities secondary to abnormal blastogenesis and characteristic of diabetic embryopathy. URSMS is also caused by abnormal blastogenesis. Therefore, this particular malformation should be viewed in the context of the multiple blastogenetic abnormalities in the cases reported here. The overlap of findings of URSMS in our cases with other abnormalities of blastogenesis, such as VATER association or sacral agenesis is not surprising, as these associations are known to lack clear diagnostic boundaries.

Phenotype of the fibroblast growth factor receptor 2 Ser351Cys mutation: Pfeiffer syndrome type III.

We present a patient with pansynostosis, hydrocephalus, seizures, extreme proptosis with luxation of the eyes out of the lids, apnea and airway obstruction, intestinal non-rotation, and severe developmental delay. His skeletal abnormalities include bilateral elbow ankylosis, radial head dislocation, and unilateral broad and deviated first toe. The phenotype of this patient is consistent with that previously reported in Pfeiffer syndrome type III, but is unusual for the lack of broad thumbs. Our patient most closely resembles the case described by Kerr et al. [1996: Am J Med Genet 66:138-143] as Pfeiffer syndrome type III with normal thumbs. Mutations in the genes for fibroblast growth factor receptors (FGFR) 1 and 2 have previously been seen in patients with Pfeiffer syndrome type I. The mutation identified in our patient, Ser351Cys in FGFR2, represents the first reported cause of Pfeiffer syndrome type III. An identical mutation was described once previously by Pulleyn et al., in a patient whose brief clinical description included cloverleaf skull, significant developmental delay, and normal hands and feet [Eur. J. Hum. Genet. 4: 283-291, 1996]. In our patient, previously performed single-strand conformation polymorphism analysis failed to detect a band shift; the mutation was identified only after independent sequence analysis.

Bilateral microtia and cleft palate in cousins with Diamond-Blackfan anemia.

We report on maternal first cousins with bilateral microtia, micrognathia, cleft palate and hematologic findings of Diamond-Blackfan anemia (DBA). The similarity of findings shared between our cases and a female reported by Hasan and Inoue [1993] suggests that this is a distinctive syndrome, rather than a chance association. DBA is a heterogeneous disorder, caused in about 25% of cases by heterozygous mutations in the RPS19 gene (DBA1). Mutation analysis in our cases did not show an RPS19 mutation, and 2 alleles were present in each. Segregation analysis for DBA1 on chromosome 19 and DBA2 on 8p23 was not consistent with linkage. We conclude that this syndrome of microtia, cleft palate and DBA is not allelic to known DBA loci.

Lateral meningocele syndrome: three new patients and review of the literature.

One female and two male patients with multiple lateral meningoceles are presented. They do not have neurofibromatosis or Marfan syndrome and share findings with the two previously described patients with multiple lateral meningoceles. The original report by Lehman et al. [1977: J Pediatr 90:49-54] was titled "familial osteosclerosis," because osteosclerosis was present in the proposita and her mother; the patient described by Philip et al. [1995: Clin Dysmorphol 4:347-351] also had increased bone density of the skull base and the sutures. Thickened calvaria were present in one of our patients; two had a prominent metopic suture. Other shared findings include multiple lateral meningoceles, Wormian bones, malar hypoplasia, downslanted palpebral fissures, a high narrow palate, and cryptorchidism in males. In addition, our patients showed ligamentous laxity, keloid formation, hypotonia, and developmental delay. A short umbilical cord was noted in two patients. One had a hypoplastic posterior arch of the atlas and an enlarged sella, as reported by Lehman et al. [1977]. Our patients appear to have the same syndrome as previously reported. We suggest it be called "lateral meningocele syndrome," because of this unique finding.

Imaging studies in a unique familial dysmyelinating disorder.

We report the imaging findings in five patients with a unique dysmyelinating disorder. MR studies of these infants showed obstructive hydrocephalus caused by mass effect produced by an enlarged cerebellum. The white matter of an enlarged cerebrum and cerebellum showed delayed myelination. Proton spectroscopy showed normal N-acetylaspartate (NAA) levels. While the dysmyelinating disorder was clearly differentiated from Canavan disease by an absence of elevated NAA and differing histopathologic findings and autosomal-dominant inheritance pattern, there were similarities to this disease in the presentation and, to some extent, in the initial imaging findings.

Clinical characteristics of patients with unicoronal synostosis and mutations of fibroblast growth factor receptor 3: a preliminary report.

Clinical teaching dictates that isolated unicoronal synostosis is sporadic in occurrence and is possibly related to intrauterine constraint. Despite this, isolated reports document a familial occurrence. It has previously been recognized that there may be a familial pattern of inheritance. Recently, mutations in fibroblast growth factor receptors (FGFRs) have been implicated in several syndromic craniosynostoses. At the authors' institution, mutations in FGFR3, located at chromosome 4p16, have been found to cause coronal synostosis. Two cases of unicoronal synostosis were found to have the same Pro250Arg missense mutation in FGFR3. This finding suggested that all patients with a diagnosis of unicoronal synostosis be screened for the FGFR3 mutation. Between January and December of 1996, patients with a diagnosis of plagiocephaly at the Children's Hospital of Philadelphia were evaluated for the FGFR3 mutation. Thirty-seven patients with unicoronal synostosis had mutational studies. Two additional patients were known to have the FGFR3 mutation at the onset of the study. Of the 37 patients screened, four were found to have the FGFR3 mutation, for a total of six patients with both unicoronal synostosis and the FGFR3 mutation. All patients with unicoronal synostosis were evaluated for facial dysmorphology and operative outcome. The six patients with the FGFR3 mutation had more severe cranial dysmorphology and were more likely to need surgical revision than those without the FGFR3 mutation. The occurrence of the FGFR3 mutation among patients with unicoronal synostosis provides evidence for a genetic basis of certain forms of plagiocephaly. The clinical, radiologic, and molecular findings will be an important addition to the surgical management and counseling of patients with unicoronal synostosis.

Bilateral duplication of the primary ulnar ossification center in Ellis-van Creveld syndrome.

A patient with Ellis-van Creveld (EvC) syndrome and bilateral duplication of the primary ulnar ossification center is presented. Abnormal ossification involving secondary ossification centers of the femur and tibia as well as duplication of primary ossification centers in the carpal bones are well described in EvC. No abnormality of ulnar ossification has been noted in patients with EvC or any other skeletal dysplasia. The occurrence of bilateral duplication of ulnar ossification centers extends the clinical findings of the EvC syndrome. The gap between the ossified areas could be misinterpreted as a fracture and thus lead to a suspicion of osteogenesis imperfecta prenatally or traumatic fracture postnatally.