Distinctive Dysmorphic Features Research Articles

STAC3 variants cause a congenital myopathy with distinctive dysmorphic features and malignant hyperthermia susceptibility.

SH3 and cysteine-rich domain-containing protein 3 (STAC3) is an essential component of the skeletal muscle excitation-contraction coupling (ECC) machinery, though its role and function are not yet completely understood. Here, we report 18 patients carrying a homozygous p.(Trp284Ser) STAC3 variant in addition to a patient compound heterozygous for the p.(Trp284Ser) and a novel splice site change (c.997-1G>T). Clinical severity ranged from prenatal onset with severe features at birth, to a milder and slowly progressive congenital myopathy phenotype. A malignant hyperthermia (MH)-like reaction had occurred in several patients. The functional analysis demonstrated impaired ECC. In particular, KCl-induced membrane depolarization resulted in significantly reduced sarcoplasmic reticulum Ca2+ release. Co-immunoprecipitation of STAC3 with CaV 1.1 in patients and control muscle samples showed that the protein interaction between STAC3 and CaV 1.1 was not significantly affected by the STAC3 variants. This study demonstrates that STAC3 gene analysis should be included in the diagnostic work up of patients of any ethnicity presenting with congenital myopathy, in particular if a history of MH-like episodes is reported. While the precise pathomechanism remains to be elucidated, our functional characterization of STAC3 variants revealed that defective ECC is not a result of CaV 1.1 sarcolemma mislocalization or impaired STAC3-CaV 1.1 interaction.

Pallister-Killian syndrome: clinical, cytogenetic and molecular findings in 15 cases

BackgroundPallister Killian syndrome (PKS, OMIM 601803) is a rare genetic disorder with a distinct phenotype caused by tissue- limited mosaicism tetrasomy of the short arm of chromosome 12, which usually cytogenetically presents as an extra isochromosome 12p.Wide phenotypic variability in PKS has been reported, ranging from pre-to perinatal death due to multiple congenital anomalies, especially diaphragmatic hernia, and classic phenotypes including seizures, severe developmental delay, macrosomia at birth, deafness, and distinct dysmorphic features, such as coarse face, temporal alopecia, a small nose with anteverted nostrils, long philtrum, and hypo−/hyper- pigmented streaks on the skin.ResultsKaryotypes obtained from cultured peripheral lymphocytes of 13 cases, who were diagnosed as PKS, were normal, while karyotypes obtained from cultured skin samples and buccal mucosa revealed the supernumerary mosaic i(12p). Mosaic karyotype was found in both fibroblast and buccal mucosa in 14 of 15 patients in our series, whereas in one stillbirth, following the clinical diagnosis of PKS, skin and buccal smear samples were taken, and all karyotypes from cultured fibroblasts revealed a supernumerary i(12p), while I-FISH study showed 60% mosaicism in mucosal cells.ConclusionsWe here share the clinical, cytogenetic and molecular cytogenetic findings of 15 cases with PKS phenotype and the parental origin of seven i(12p) identified by molecular analyses. To our knowledge, this is the largest series of PKS patients with parental origin study from a single center. We believe that our study makes a significant contribution to the literature because we specifically found no differences in the phenotypes of cases with either a maternal or paternal origin of the extra element and differential imprinting appeared not to be a factor.

Expanding the Oro-Dental and Mutational Spectra of Kabuki Syndrome and Expression of KMT2D and KDM6A in Human Tooth Germs.

Kabuki syndrome is a rare genetic disorder characterized by distinct dysmorphic facial features, intellectual disability, and multiple developmental abnormalities. Despite more than 350 documented cases, the oro-dental spectrum associated with kabuki syndrome and expression of KMT2D (histone-lysine N-methyltransferase 2D) or KDM6A (lysine-specific demethylase 6A) genes in tooth development have not been well defined. Here, we report seven unrelated Thai patients with Kabuki syndrome having congenital absence of teeth, malocclusion, high-arched palate, micrognathia, and deviated tooth shape and size. Exome sequencing successfully identified that six patients were heterozygous for mutations in KMT2D, and one in KDM6A. Six were novel mutations, of which five were in KMT2D and one in KDM6A. They were truncating mutations including four frameshift deletions and two nonsense mutations. The predicted non-functional KMT2D and KDM6A proteins are expected to cause disease by haploinsufficiency. Our study expands oro-dental, medical, and mutational spectra associated with Kabuki syndrome. We also demonstrate for the first time that KMT2D and KDM6A are expressed in the dental epithelium of human tooth germs.

Novel intragenic deletions within the UBE3A gene in two unrelated patients with Angelman syndrome: case report and review of the literature

BackgroundPatients with Angelman syndrome (AS) are affected by severe intellectual disability with absence of speech, distinctive dysmorphic craniofacial features, ataxia and a characteristic behavioral phenotype. AS is caused by the lack of expression in neurons of the UBE3A gene, which is located in the 15q11.2-q13 imprinted region. Functional loss of UBE3A is due to 15q11.2-q13 deletion, mutations in the UBE3A gene, paternal uniparental disomy and genomic imprinting defects.Case presentationWe report here two patients with clinical features of AS referred to our hospital for clinical follow-up and genetic diagnosis. Methylation Specific-Multiplex Ligation-Dependent Probe Amplification (MS-MLPA) of the 15q11.2-q13 region was carried out in our laboratory as the first diagnostic tool detecting two novel UBE3A intragenic deletions. Subsequently, the MLPA P336-A2 kit was used to confirm and determine the size of the UBE3A deletion in the two patients. A review of the clinical features of previously reported patients with whole UBE3A gene or partial intragenic deletions is presented here together with these two new patients.ConclusionAlthough rare, UBE3A intragenic deletions may represent a small fraction of AS patients without a genetic diagnosis. Testing for UBE3A intragenic exonic deletions should be performed in those AS patients with a normal methylation pattern and no mutations in the UBE3A gene.

Clinical and Molecular Characterization of Prader-Willi Syndrome.

To describe the clinical presentations and molecular diagnosis to aid the clinicians in early diagnosis and appropriate management of Prader-Willi syndrome (PWS). Thirty-four clinically diagnosed PWS cases were enrolled after obtaining informed consent/assent. Demographic details, clinical data and anthropometry were recorded using structured proforma. The facial dysmorphology was evaluated. Appropriate genetic testing was performed to confirm the diagnosis. At diagnosis, the most common clinical features included obesity (59%) and short stature (53%). Distinct dysmorphic features were observed in 67%. Neonatal hypotonia with feeding difficulty, delayed development in infancy and childhood behavioral problems were reported in 94%, 94% and 74% respectively. Food seeking behavior and hyperphagia was reported in 67%. Seizures were reported in 47%. All children had underdeveloped external genitalia. Growth hormone (GH) deficiency and impaired glucose tolerance were found in 56% and 50% respectively. Sleep related problems were seen in 67%. Skin and rectal picking were reported in 67%. FISH confirmed micro-deletion was found in 64.7% and abnormal methylation in 35%, of which uniparental disomy was confirmed in 14.7%. Clinical suspicion is vital for early detection of PWS. Confirmation of the diagnosis requires complex multi-tier molecular genetic testing.

OD08 - STAC3 p.Trp284Ser associated with congenital myopathy with distinctive dysmorphic features and malignant hyperthermia

OD08 - STAC3 p.Trp284Ser associated with congenital myopathy with distinctive dysmorphic features and malignant hyperthermia

Early Infantile Epileptic Encephalopathy with a de novo variant in ZEB2 identified by exome sequencing

Early Infantile Epileptic Encephalopathy (EIEE) presents shortly after birth with frequent, severe seizures, a burst-suppression EEG pattern, and progressive disturbance of cerebral function. We present a case of EIEE associated with a de novo missense variant in ZEB2. Heterozygous truncating mutations or deletions in ZEB2 are known to cause Mowat-Wilson syndrome (MWS), which is characterized by seizures with onset in the second year of life, distinctive dysmorphic facial features and malformations that were absent in this patient. This unique case expands the range of phenotypes associated with variants in ZEB2 and indicates that this gene should be included in the molecular investigation of EIEE cases.

19q13.32 microdeletion syndrome: Three new cases

A previous report described a unique phenotype associated with an apparently de novo 732 kb 19q13.32 microdeletion, consisting of intellectual disability, facial asymmetry, ptosis, oculomotor abnormalities, orofacial clefts, cardiac defects, scoliosis and chronic constipation. We report three unrelated patients with developmental delay and dysmorphic features, who were all found to have interstitial 19q13.32 microdeletions of varying sizes. Both the previously reported patient and our Patient 1 with a larger, 1.3-Mb deletion have distinctive dysmorphic features and medical problems, allowing us to define a recognizable 19q13.32 microdeletion syndrome. Patient 1 was hypotonic and dysmorphic at birth, with aplasia of the posterior corpus callosum, bilateral ptosis, oculomotor paralysis, down-slanting palpebral fissures, facial asymmetry, submucosal cleft palate, micrognathia, wide-spaced nipples, right-sided aortic arch, hypospadias, bilateral inguinal hernias, double toenail of the left second toe, partial 2–3 toe syndactyly, kyphoscoliosis and colonic atony. Therefore, the common features of the 19q13.32 microdeletion syndrome include facial asymmetry, ptosis, oculomotor paralysis, orofacial clefting, micrognathia, kyphoscoliosis, aortic defects and colonic atony. These findings are probably related to a deletion of some combination of the 20–23 genes in common between these two patients, especially NPAS1, NAPA, ARHGAP35, SLC8A2, DHX34, MEIS3, and ZNF541. These candidate genes are expressed in the brain parenchyma, glia, heart, gastrointestinal tract and musculoskeletal system and likely play a fundamental role in the expression of this phenotype. This report delineates the phenotypic spectrum associated with the haploinsufficiency of genes found in 19q13.32.

Andersen-Tawil syndrome (LQT7) is associated with alterations in left ventricular rotational mechanics

E-mail: nemes.attila@med.u-szeged.hu The goal: Andersen-Tawil syndrome (ATS), also called Andersen Syndrome and Long QT Syndrome 7 (LQT7) is a rare condition. ATS is characterized by episodic flaccid muscle weakness, distinctive dysmorphic features, ventricular arrhythmias and prolonged QT interval in the presence of normal conventional left ventricular (LV) structural and functional parameters. In the normal heart, the LV base rotates clockwise, while the apex rotates counterclockwise during systole, producing a towel-wringing motion of the heart. The difference between the LV base and LV apex is called net twist angle. The present study was designed to assess LV rotational mechanics in ATS by three-dimensional speckle-tracking echocardiography (3DSTE). Patients and Methods: The study comprised 6 patients with ATS, their results were compared to 20 healthy volunteers. Complete two-dimensional Doppler echocardiography and 3DSTE were performed in all cases. 3DSTE was used to measure apical and basal LV rotations and LV twist. Results: During 3DSTE, apical LV rotation proved to be 8.43 ± 1.54 degree, while basal LV rotation was -2.31 ± 1.31 degree, therefore LV twist was 11.12 ± 5.32 degree in healthy subjects. In 3 out of 6 ATS patients, LV basal and LV apical rotation were in the same direction resulting in the near absence of LV twist showing „rigid body rotation”. In the remaining 3 ATS patients, LV apical rotation (2.06 ± 1.30 degree, p <0.05) together with LV twist (6.51 ± 1.28 degree, p <0.05) were significantly decreased as compared to controls. Mean basal rotation showed no significant difference compared to the values of controls (-4.45 ± 1.87 degree, p =NS). Conclusions: Significant alterations in LV rotational mechanics could be demonstrated in ATS by 3DSTE.

Novel MLL2 Mutation in Kabuki Syndrome With Hypogammaglobulinemia and Severe Chronic Thrombopenia

Kabuki syndrome is a rare condition characterized by distinct dysmorphic features and a broad spectrum of organ anomalies. Differentiating it from other syndromes can be difficult, particularly in patients with incomplete phenotypic manifestation. Recently, MLL2 gene mutations were identified as the underlying genetic cause of Kabuki syndrome in the majority of cases. We report the case of an adolescent with an uncommon combination of manifestations, including hypogammaglobulinemia and severe chronic thrombopenia associated with a novel MLL2 mutation. This report adds to the growing knowledge on the mutational and phenotypic spectrum of Kabuki syndrome.

Report of interstitial 22q13.1q13.2 microduplication in two siblings with distinctive dysmorphic features, heart defect and mental retardation

We present two siblings (a boy and a girl) with a submicroscopic 4 Mb duplication at 22q13.1q13.2. Both children manifested infantile hypotonia and delayed motor milestones, congenital heart defect, growth deficiency, and strikingly similar and distinctive craniofacial dysmorphism including brachycephaly, blepharophimosis, short broad-based nose and wide mouth with thin upper lip. The boy had also a submucous cleft palate. Both had fair skin and hair compared with their parents. Both had moderate mental retardation associated with a short attention span. A 4-Mb interstitial duplication at 22q13.1q13.2 was detected by whole genome microarray comparative genomic hybridisation (array CGH) in both children. The duplication was confirmed by fluorescence in situ hybridisation (FISH) analysis. Their parents had normal array CGH results. FISH analysis revealed that the father was a carrier of a balanced interchromosomal submicroscopic insertion of 22q13 into chromosome 11q23, explaining the unbalanced aberration detected in both children. This report narrows down the critical region at 22q13.1q13.2, which is associated with mental retardation, pre- and post-natal growth retardation, hippocampal malformation, psychiatric symptoms such as short attention span and facial dysmorphism including hypertelorism, epicanthal folds and low set/abnormal ears.

Growth retardation, intellectual disability, facial anomalies, cataract, thoracic hypoplasia, and skeletal abnormalities: A novel phenotype

We report on a 14-year-old girl with growth deficiency, microcephaly, intellectual disability, distinctive dysmorphic features (bulbous nose with wide nasal base, hypotelorism, deeply set eyes, protruding cupped ears, and thick lower lip), cataract, pigmentary retinopathy, hypoplastic thorax, kyphoscoliosis, and unusual skeletal changes but without chromosomal imbalances detected by array-CGH who probably represents a novel phenotype.

Further delineation of novel 1p36 rearrangements by array-CGH analysis: Narrowing the breakpoints and clarifying the “extended” phenotype

High resolution oligonucleotide array Comparative Genome Hybridization technology (array-CGH) has greatly assisted the recognition of the 1p36 contiguous gene deletion syndrome. The 1p36 deletion syndrome is considered to be one of the most common subtelomeric microdeletion syndromes and has an incidence of ~1 in 5000 live births, while respectively the “pure” 1p36 microduplication has not been reported so far.We present seven new patients who were referred for genetic evaluation due to Developmental Delay (DD), Mental Retardation (MR), and distinct dysmorphic features. They all had a wide phenotypic spectrum. In all cases previous standard karyotypes were negative. Array-CGH analysis revealed five patients with interstitial 1p36 microdeletion (four de novo and one maternal) and two patients with de novo reciprocal duplication of different sizes. These were the first reported “pure” 1p36 microduplication cases so far. Three of our patients carrying the 1p36 microdeletion syndrome were also found to have additional pathogenetic aberrations. These findings (del 3q27.1; del 4q21.22–q22.1; del 16p13.3; dup 21q21.2–q21.3; del Xp22.12) might contribute to the patients' severe phenotype, acting as additional modifiers of their clinical manifestations. We review and compare the clinical and array-CGH findings of our patients to previously reported cases with the aim of clearly delineating more accurate genotype–phenotype correlations for the 1p36 syndrome that could allow for a more precise prognosis.

Delineation of the interstitial 6q25 microdeletion syndrome: Refinement of the critical causative region

Interstitial deletions of the long arm of chromosome 6 are rare. Clinically, this is a recognizable microdeletion syndrome associated with intellectual disability (ID), acquired microcephaly, typical dysmorphic features, structural anomalies of the brain, and nonspecific multiple organ anomalies. Most of the reported cases have cytogenetically visible interstitial deletions or subtelomeric microdeletions. We report on a boy with global developmental delay, distinct dysmorphic features, dysgenesis of the corpus callosum, limb anomalies, and genital hypoplasia who has a small interstitial deletion of the long arm of chromosome 6 detected by comparative genomic hybridization (CGH). The deleted region spans around 1 Mb of DNA and contains only two coding genes, ARID1B and ZDHHC14. To the best of our knowledge, this case represents the typical phenotype with the smallest deletion reported so far. We discuss the possible role of these genes in the phenotypic manifestations.

2q23.1 microdeletion of the MBD5 gene in a female with seizures, developmental delay and distinct dysmorphic features

We report a 2-year-old female who initially presented with seizures, developmental delay and dysmorphic features and was found to have a 0.3 Mb deletion at chromosome 2q23.1 encompassing the critical seizure gene, MBD5. Her distinct physical features include bifrontal narrowing with brachycephaly, low anterior hairline, hypotonic facial features with short upturned nose, flat nasal bridge, hypertelorism, tented upper lip with everted lower lip, downturned corners of her mouth, and relatively coarse facial features including thickened tongue. She also had a short neck, brachytelephalangy, clinodactyly, and hypertrichosis. At 3½ years she developed progressive ataxia and lost vocabulary at the age of 4. Regression has been reported in one other case of MBD5 deletion. MBD5 is a member of the methyl binding gene family and appears to be responsible for regulating DNA methylation in the central nervous system. Our patient was entirely deleted for the MBD5 gene with partial loss of the EPC2 gene, which suggests that haploinsufficiency of MBD5 is responsible for the distinct phenotype observed. This supports the hypothesis that MBD5 is indeed the critical gene implicated for the findings seen in patients with deletions of chromosome 2q23.1. Further studies are necessary to delineate the role that the MBD5 gene plays in the development of the brain and these specific physical characteristics.

Clinical and Polygraphic Improvement of Breathing Abnormalities After Valproate in a Case of Pitt-Hopkins Syndrome

Pitt-Hopkins syndrome is a rare genetic form of severe psychomotor delay, caused by mutations in transcription cell factor-4 gene and characterized by distinctive dysmorphic features and abnormal breathing pattern. The current report describes the polygraphic features of the syndrome's typical breathing pattern in a patient both in wakefulness and in sleep. The control of these breathing alterations is important to prevent the neurological sequelae linked to chronic cerebral hypoxemia in early ages. No data are available on effective treatment options for breathing abnormalities of Pitt-Hopkins syndrome. The authors polygraphically documented a reduction of apneic and hypopneic phenomena, with a significant improvement in saturation values, after the introduction of sodium valproate.

2q23.1 microdeletion of the MBD5 gene in a female with seizures, developmental delay and distinct dysmorphic features

We report a 2-year-old female who initially presented with seizures, developmental delay and dysmorphic features and was found to have a 0.3 Mb deletion at chromosome 2q23.1 encompassing the critical seizure gene, MBD5. Her distinct physical features include bifrontal narrowing with brachycephaly, low anterior hairline, hypotonic facial features with short upturned nose, flat nasal bridge, hypertelorism, tented upper lip with everted lower lip, downturned corners of her mouth, and relatively coarse facial features including thickened tongue. She also had a short neck, brachytelephalangy, clinodactyly, and hypertrichosis. At 3½ years she developed progressive ataxia and lost vocabulary at the age of 4. Regression has been reported in one other case of MBD5 deletion. MBD5 is a member of the methyl binding gene family and appears to be responsible for regulating DNA methylation in the central nervous system. Our patient was entirely deleted for the MBD5 gene with partial loss of the EPC2 gene, which suggests that haploinsufficiency of MBD5 is responsible for the distinct phenotype observed. This supports the hypothesis that MBD5 is indeed the critical gene implicated for the findings seen in patients with deletions of chromosome 2q23.1. Further studies are necessary to delineate the role that the MBD5 gene plays in the development of the brain and these specific physical characteristics.

Ehlers–Danlos arthrochalasia type (VIIA–B) – expanding the phenotype: from prenatal life through adulthood

The Ehlers-Danlos syndromes (EDS) form a clinically and genetically heterogeneous group of inherited connective-tissue disorders characterized by joint hypermobility, tissue fragility and skin abnormalities. Six subtypes have been well characterized based on clinical features and molecular genetic abnormalities. The arthrochalasia type EDS (formerly types VIIA and B) is characterized by severe generalized joint hypermobility with multiple dislocations including congenital bilateral dislocation of the hips, muscular hypotonia and distinct dysmorphic features. The diagnosis of the arthrochalasia type EDS is of importance in the neonatal period because of consequences of physical disability in later life. However, the differential diagnosis may be difficult because of overlap with other hypermobility syndromes. In addition, the significant hypotonia may direct the physician toward various neuromuscular diagnoses. As patients become older, the hypotonia decreases and facial features become less distinct. In this report, we describe seven patients at different ages. Timing of diagnosis varied from prenatal life to adult age. The diagnosis of EDS type VII was confirmed by biochemical studies or mutation analysis showing characteristic mutations in COL1A1 and COL1A2. These mutations result in skipping of exon 6, which leads to defective collagen synthesis. For physicians treating patients with EDS type VII, achieving mobility for the patient is the greatest challenge and it may be impossible because of recurrent dislocations of nearly all joints in severe cases.

Craniosynostosis in patients with Noonan syndrome caused by germline KRAS mutations

Craniosynostosis, the premature fusion of one or more cranial sutures, is a developmental defect that disrupts the cranial morphogenetic program, leading to variable dysmorphic craniofacial features and associated functional abnormalities. Craniosynostosis is frequently observed as an associated feature in a number of clinically and genetically heterogeneous syndromic conditions, including a group of disorders caused by activating mutations in genes coding for the fibroblast growth factor receptor family members FGFR1, FGFR2, and FGFR3. In these disorders, dysregulation of intracellular signaling promoted by the aberrant FGFR function is mediated, at least in part, by the RAS-MAPK transduction pathway. Mutations in KRAS, HRAS, and other genes coding for proteins participating in this signaling cascade have recently been identified as underlying Noonan syndrome (NS) and related disorders. While cardinal features of these syndromes include distinctive dysmorphic facial features, reduced growth, congenital heart defects, and variable ectodermal anomalies and cognitive impairment, craniosynostosis is not a recognized feature. Here, we report on the occurrence of premature closure of cranial sutures in subjects with NS, and their specific association with mutations in the KRAS gene. These findings highlight the pathogenetic significance of aberrant signaling mediated by the RAS signaling pathway in other known forms of craniosynostosis, and suggest that, even in the absence of radiologically demonstrable synostosis of the calvarian sutures, dysregulated growth and/or suture closure at specific craniofacial sites might contribute to the craniofacial anomalies occurring in NS.

A de novo apparently balanced translocation [46,XY,t(2;9)(p13;p24)] interrupting RAB11FIP5 identifies a potential candidate gene for autism spectrum disorder

Autism spectrum disorder (ASD) is a severe developmental disorder of the central nervous system characterized by impairments in social interaction, communication, and range of interests and behaviors. The syndrome's prevalence is estimated to be as high as 1 in 150 American children yet its etiology remains largely unknown. Examination of observed cytogenetic variants in individuals with ASD may identify genes involved in its pathogenesis. As part of a multidisciplinary study, an apparently balanced de novo translocation between chromosomes 2 and 9 [46,XY,t(2;9)(p13;p24)] was identified in a subject with pervasive developmental disorder not otherwise specified (PDD-NOS), and no distinctive dysmorphic features. Molecular characterization of the rearrangement revealed direct interruption of the RAB11 family interacting protein 5 (RAB11FIP5) gene. RAB11FIP5 is a Rab effector involved in protein trafficking from apical recycling endosomes to the apical plasma membrane. It is ubiquitously expressed and reported to contribute to both neurotransmitter release and neurotransmitter uptake at the synaptic junction. Detailed analysis of the rearrangement breakpoints suggests that the reciprocal translocation may have formed secondary to incorrect repair of double strand breaks (DSBs) by nonhomologous end-joining (NHEJ).