Malformations in infants of diabetic mothers

Review of Evidence for Environmental Causes of Uveal Coloboma

Uveal coloboma is a condition defined by missing ocular tissues and is a significant cause of childhood blindness. It occurs from a failure of the optic fissure to close during embryonic development,and may lead to missing parts of the iris, ciliary body, retina, choroid, and optic nerve. Because there is no treatment for coloboma, efforts have focused on prevention. While several genetic causes of coloboma have been identified, little definitive research exists regarding the environmental causes of this condition. We review the current literature on environmental factors associated with coloboma in an effort to guide future research and preventative counseling related to this condition.

Mutations specific to the Rac-GEF domain of TRIO cause intellectual disability and microcephaly

BACKGROUND

Neurodevelopmental disorders have challenged clinical genetics for decades, with over 700 genes implicated and many whose function remains unknown. The application of whole-exome sequencing is proving pivotal in closing the genotype/phenotype gap through the discovery of new genes and variants that help to unravel the pathogenic mechanisms driving neuropathogenesis. One such discovery includes TRIO, a gene recently implicated in neurodevelopmental delay. Trio is a Dbl family guanine nucleotide exchange factor (GEF) and a major regulator of neuronal development, controlling actin cytoskeleton dynamics by activating the GTPase Rac1.

METHODS

Whole-exome sequencing was undertaken on a family presenting with global developmental delay, microcephaly and mild dysmorphism. Father/daughter exome analysis was performed, followed by confirmatory Sanger sequencing and segregation analysis on four individuals. Three further patients were recruited through the deciphering developmental disorders (DDD) study. Functional studies were undertaken using patient-specific Trio protein mutations.

RESULTS

We identified a frameshift deletion in TRIO that segregated autosomal dominantly. By scrutinising data from DDD, we further identified three unrelated children with a similar phenotype who harboured de novo missense mutations in TRIO. Biochemical studies demonstrated that in three out of four families, the Trio mutations led to a markedly reduced Rac1 activation.

CONCLUSIONS

We describe an inherited global developmental delay phenotype associated with a frameshift deletion in TRIO. Additionally, we identify pathogenic de novo missense mutations in TRIO associated with the same consistent phenotype, intellectual disability, microcephaly and dysmorphism with striking digital features. We further functionally validate the importance of the GEF domain in Trio protein function. Our study demonstrates how genomic technologies are yet again proving prolific in diagnosing and advancing the understanding of neurodevelopmental disorders.

Caudal dysplasia, femoral hypoplasia-unusual facies syndrome and absent radius: a new association in infant of diabetic mother?

The Caudal dysplasia syndrome (CDS) and the femoral hypoplasia-unusual facies syndrome (FHUFS) have been reported to be more frequent among infants of diabetic mothers (IDMs). Infact, uncontrolled maternal diabetes is the most common cause of both the syndromes. Till now, there is no case report to suggest absent radius as a manifestation of IDMs. The authors report a rare case of newborn, who presented with features compatible with both CDS and FHUFS with an additional feature of absent radius, which is not reported in the literature so far. The possibility that all these features represent different manifestations of the same disorder is discussed here.

Genetic syndromes involving hearing

OBJECTIVE

The fundamental processes involved in the mechanism of hearing seem to be controlled by hundreds of genes and hereditary hearing impairment may be caused by a large variety of genetic mutations in different genes. Approximately 150 loci for monogenic syndromic and non-syndromic hearing impairment (HI) disorders have been mapped to the human genome. The identification of these genes and functional analysis of the proteins they encode, are paving the way towards a better understanding of the physiology and pathophysiology of the auditory system. To date, approximately 50 causative genes have been identified.

METHODS

The clinical and neuroradioldical findings of syndromal hearing impairment are analysed.

RESULTS

This paper presents an updated report on genetic syndromes in which a hearing impairment is involved, with a particular attention to the ones associated with external ear and craniofacial malformations.

CONCLUSIONS

Concepts in human genetics are rapidly evolving together with technologies. The concept itself of gene is changing. A genetic diagnosis of syndromal hearing impairment has many practical consequences: it can implies specific prognosis, specific management, specific recurrence risk in relatives and, if the diagnosis is confirmed at the molecular level, possibility of a specific early prenatal diagnosis for severe syndromes. It is important to highlight the necessity that the pediatric otolaryngologist must have a close collaboration with a clinical geneticist and a neuroradiologist.

Syndromes of the first and second pharyngeal arches: A review

Our aim in this review is to discuss currently known mechanisms associated with three important syndromes of the first and second pharyngeal arches: Treacher Collins syndrome (TCS), Oculo-auriculo-vertebral syndrome (AOVS) and Auriculo-Condylar syndrome (ACS) or question mark ear syndrome. TCS and ACS are autosomal dominant diseases, with nearly complete penetrance and wide spectrum of clinical variability. The phenotype of the latter has several overlapping features with OAVS, but OAVS may exist in both sporadic and autosomal dominant forms. Mutations in the TCOF1 gene are predicted to cause premature termination codons, leading to haploinsuficiency of the protein treacle and causing TCS. Low amount of treacle leads ultimately to a reduction in the number of cranial neural crest cells migrating to the first and second pharyngeal arches. Other than TCS, the genes associated with ACS and OAVS are still unknown. The first locus for ACS was mapped by our group to 1p21-23 but there is genetic heretogeneity. Genetic heterogeneity is also present in OAVS. Based on the molecular analysis of balanced translocation in an OAVS patient, it has been suggested that abnormal expression of BAPX1 possibly due to epigenetic disregulation might be involved with the etiology of OAVS. Involvement of environmental events has also been linked to the causation of OAVS. Identification of factors leading to these disorders are important for a comprehensive delineation of the molecular pathways underlying the craniofacial development from the first and the second pharyngeal arches, for genetic counseling and to open alternative strategies for patient treatment.

Oculo-auriculo-vertebral spectrum: associated anomalies, functional deficits and possible developmental risk factors

Swedish patients with the oculo-auriculo-vertebral (OAV) spectrum participated in a prospective multidisciplinary investigation. The aims of the study were to describe their systemic and functional defects, especially autism spectrum disorders, and to search for possible etiologic risk factors. Available medical records were studied and the mothers answered a questionnaire on history of prenatal events. A clinical examination evaluating systemic findings, vision, hearing, speech, oral and swallowing function, and neuropsychiatric function, especially autism, was made. Eighteen patients, (11 males, 7 females) aged 8 months to 17 years with OAV were studied. Most frequent systemic malformations included, ear abnormalities (100%), ocular malformations (72%), vertebral deformities (67%), cerebral anomalies (50%), and congenital heart defects (33%). Functional defects consisted of hearing impairment (83%), visual impairment (28%), both visual and hearing impairment (28%), difficulties in feeding/eating (50%), speech (53%), mental retardation (39%), and severe autistic symptoms (11%). Three children were born following assisted fertilization (two intracytoplasmatic sperm injection, one in vitro fertilization), two mothers reported early bleedings, and six (33%) mothers had smoked during pregnancy.

Severe fatal course of axial mesodermal dysplasia spectrum associated with complex cardiac defect in an infant of a mother with insulin dependent diabetes

Axial mesodermal dysplasia spectrum (AMDS) includes the features of other malformation complexes or sequences, such as oculo-auriculo-vertebral spectrum (OAVS) and sacral dysgenesis. We describe a new patient, an infant born to a type 1 diabetic mother, with the phenotype of AMDS as well as severe congenital cardiac anomalies including transposition of the great arteries and an atrioventricular septal defect. Congenital heart defects had been reported with OAVS, sacral dysgenesis, and in an infant born to a diabetic mother and combinations of these findings have been reported in the same patient. To our knowledge, this is the first patient with AMDS with transposition of great arteries and an atrioventricular septal defect and the second patient with AMDS who had history of parental consanguinity. The mechanism through which maternal diabetes mellitus leads to malformations is not entirely clear, but the glycemic control is essential in the care of mothers.

CHARGE syndrome: an update

CHARGE syndrome is a rare, usually sporadic autosomal dominant disorder due in 2/3 of cases to mutations within the CHD7 gene. The clinical definition has evolved with time. The 3C triad (Coloboma-Choanal atresia-abnormal semicircular Canals), arhinencephaly and rhombencephalic dysfunctions are now considered the most important and constant clues to the diagnosis. We will discuss here recent aspects of the phenotypic delineation of CHARGE syndrome and highlight the role of CHD7 in its pathogeny. We review available data on its molecular pathology as well as cytogenetic and molecular evidences for genetic heterogeneity within CHARGE syndrome.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.

Experimental mechanisms of diabetic embryopathy and strategies for developing therapeutic interventions

A high frequency of birth defects is seen in infants born to diabetic mothers. The mechanisms by which maternal hyperglycemia, the major teratogenic factor, induces embryonic malformations remain to be addressed. It has been shown that increases in programmed cell death are one of the factors causing embryonic malformations. Hyperglycemia-induced apoptosis is associated with oxidative stress, lipid peroxidation, and decreased antioxidant defense capacity in the embryos. Recent studies have revealed that mitogen-activated protein kinases as intracellular signaling factors are involved in hyperglycemia-induced embryopathy. Based on the findings, interventions to prevent embryonic malformations have been explored. Strategies include supplementation of molecules that are deficient in the embryos under hyperglycemic conditions and antioxidants to alleviate the adverse effects of oxidative stress. The ultimate goal is to develop multi-nutrient dietary supplements to eliminate embryonic abnormalities induced by maternal diabetes.

Hearing screening outcomes in infants of pregestational diabetic mothers

PURPOSE

Hearing screening results for newborns of diabetic mothers were compared with those of nondiabetic controls.

METHOD

This study was a retrospective chart review of mothers with pregestational diabetes mellitus and their neonates (n=73) who received newborn hearing screening between January 1, 2000, and May 1, 2002. A group of nondiabetic mothers and their infants (n=73), with birth dates that matched the diabetic group, served as controls. A 2-tiered hearing screening protocol, employing distortion product otoacoustic emission (DPOAE) and automated auditory brainstem response (A-ABR) screening techniques, was used.

RESULTS

The DPOAE screening failure rate was 5.5% (4/73) for babies in the nondiabetic control group and 11.0% (8/73) for infants of diabetic mothers; this difference was not statistically significant. The A-ABR failure rate was 9.1% (1/11) for the diabetic group compared with 0% (0/4) for the controls, but the A-ABR was measured for only a small number of participants in each group. The frequency of premature birth and abnormal birth weight was significantly greater for the infants of diabetic mothers compared with controls.

CONCLUSIONS

Given the greater frequency of prematurity and abnormal birth weight in the population of neonates born to diabetics, additional research using A-ABR is recommended.

A newly recognized syndrome involving limbs, pelvis, and genital organs or a variant of Al-Awadi/Raas-Rothschild syndrome?

We report on a 3-year-old Thai boy with limb, pelvic, and genital malformations. The combination of findings found in this patient is similar to that of Al-Awadi/Raas-Rothchild syndrome (AARRS) or limb/pelvis hypoplasia/aplasia syndrome. The upper limbs are more severely affected than the lower ones. Unlike that of AARRS, the radial ray is more severely affected than the ulnar ray. The presence of humeroulnar synostosis and humero-ulnar-radial synostosis and the absence of a radius distinguishes it from AARRS. The similarities and dissimilarities between the features in the present patient and other limb-pelvic hypoplasia/aplasia syndromes are discussed. The findings in this group of patients appear to demonstrate limb-pelvis-genital organ developmental field defects.

Unilateral bowing of long bones and multiple congenital anomalies in a child born to a mother with gestational diabetes

We report on a new-born girl with multiple congenital anomalies consisting of major skeletal anomalies restricted to the left side, cleft palate, ventricular and atrial septal defect, retromicrognathia, short neck, dysplastic low-set ears and large birth weight. The left-side bony anomalies include shortening and bowing of the femur and tibia, hypoplasia of the fibula, hip dislocation, clubfoot and mild shortening of the long tubular bones in the left arm with elbow dislocation. The pregnancy was complicated by insulin-dependent gestational diabetes mellitus in the mother. The radiographic features were not consistent with the diagnosis of campomelic dysplasia, kyphomelic dysplasia or other skeletal dysplasias characterized by bowing and shortening of the long bones. To our knowledge, the multiple congenital anomalies, including major skeletal malformations, present in our case have never been simultaneously reported until now. A maternal diabetes syndrome in this infant is probable. The occurrence of major congenital malformations in offspring of women with gestational diabetes is reviewed and discussed. We provide evidence that gestational diabetes mellitus could be teratogenic. We recommend a careful diabetic control in every woman with a history of gestational diabetes.

Mandibular malformations: growth characteristics and management in hemifacial microsomia and Nager syndrome

This review article describes normal and abnormal development of the mandible. The focus is on the characteristics of the mandible and its attached muscles in the various types of hemifacial microsomia and in Nager syndrome. Management protocols for these two types of malformations are presented in relation to development stages.

Branchio-oto (BO) syndrome and oculo-auriculo-vertebral phenotype: overlapping clinical findings in a child from a BO family

A three-generation BO family is presented: the proband showed, in addition to branchio-oto malformations, a severe condition with growth retardation, mandibular hypoplasia and vertebral anomalies resembling the oculo-auriculo-vertebral (OAV) phenotype. This family study supports the hypothesis of Rollnick and Kaye that the OAV spectrum may represent, in some cases, an extreme component of the BOR syndrome. The finding has relevant implications for genetic counselling regarding both conditions.

Bilateral radial deficiency with lower limb involvement

We describe a 10-month-old boy with an unclassified form of radial aplasia with absent thumbs, tibia hypo/-aplasia, and partial absence of toes. Only a few cases with similar limb deficiencies have been published. We try to classify the malformations on the basis of embryological considerations and discuss possible differential diagnosis.

Trisomy 22 and facioauriculovertebral (Goldenhar) sequence

We report on an infant girl born with complete trisomy 22 and left hemifacial microsomia, ear anomaly, and limbal and epibulbar complex choristoma. Trisomy 22 was confirmed by prometaphase chromosome analysis and in situ hybridization. This patient extends the list of chromosome abnormalities associated with apparent Golenhar sequence and emphasizes the importance of chromosome analysis in the investigation of patients with this condition. A detailed ophthalmopathological investigation is reported.

Goldenhar syndrome and autistic behaviour

Two girls with concomitant Goldenhar syndrome (oculo-auriculovertebral spectrum disorder) and autistic disorder are described. One was diagnosed as having Goldenhar syndrome in the first few weeks of life and as having autistic disorder in her fifth year; the other was diagnosed as having Goldenhar syndrome when she was referred for evaluation of autistic symptoms at seven years of age. The type of physical abnormalities encountered in Goldenhar syndrome suggests damage to neural structures in the second or late stages of the first trimester. The two cases described in this report suggest that autistic disorder sometimes can result from neural damage during the second trimester.

Update of sporadic microphthalmos and coloboma. Non-inherited anomalies

The majority of patients with microphthalmos and colobomas have genetic disorders. This is a survey of non-inherited, sporadic microphthalmos. Such cases may occur in the Goldenhar, CHARGE and VATER associations; it may also be due to teratological agents, for instance maternal ingestion of drugs, maternal infection, fever or irradiation. In these cases it is possible that neural crest cell development is abnormal. Some drugs, for instance retinoic acid are regulators of Hox genes which control an ordered sequence of differentiation; coloboma or microphthalmos may appear if deregulation occurs. Large choristomas of the anterior segment of the eye may be associated with microphthalmos or anophthalmos. Encephaloceles or orbital tumours may deform the growing eye and are another cause of non-inherited microphthalmos.

Hemifacial microsomia: developmental consequence of perturbation of the auriculofacial cartilage model?

The cause of hemifacial microsomia (HFM) is currently the subject of much investigation. Despite a large body of clinical and experimental data, little is certain other than the heterogeneity of this malformation complex. Here we suggest that some of the cases previously designated as being multifactorial in origin may be interpreted instead as resulting from a single-gene mutation, by applying a stochastic single-gene model. A variety of models of the pathogenesis of HFM have been described, including the proposal that local embryonic haemorrhage is a causal mechanism. More recently, it has been suggested that an interference in chondrogenesis is primarily responsible for the HFM phenotype. In this paper direct experimental evidence, based on surgical interference of mandibular development in the chick embryo, is applied in favour of the latter concept. In particular, asymmetrical perturbation of Meckel's cartilage has been shown to result in asymmetry of the mandible, and it is proposed that, irrespective of cause, the skeletal pathogenesis of HFM primarily involves the auriculofacial cartilage model.

Generalized chondrodysplasia punctata with shortness of humeri and brachymetacarpy: humero-metacarpal (HM) type: variation or heterogeneity?

We report on a girl with symmetrical rhizomelic shortness of the upper limbs and punctate epiphyseal calcifications noted at birth. Presumably she has normal height, but short nose, short hands, and normal mentation; and on roentgenograms short and wide humeri, symmetrical brachymetacarpy, especially of the 4th metacarpals, and hypoplastic distal phalanges, sagittal clefting of vertebral bodies, and punctate calcifications at various areas including the entire spine, sacrum, hands, feet, trachea, and thyroid cartilage. It is an apparently new syndrome of chondrodysplasia punctata (CP), quite distinct from the classic form (Conradi-Hünermann type), as well as the other well-defined forms of CP. We thus suggest the term chondrodysplasia punctata, humero-metacarpal (HM) type.

Sporadic, idiopathic MCA syndrome with mandibulofacial dysostosis and tibial hemimelia

We report on a Brazilian woman with mandibulofacial dysostosis, cleft lip/palate, vertebral anomalies, abnormally modeled femora, and bilateral tibial agenesis. The clinical aspects involving this patient strongly suggest an unreported condition. Clinical and genetic aspects are discussed.

Concordance of auriculo-cardiovascular-skeletal malformations: a new malformation complex in an infant of a diabetic mother?

The incidence of malformations among infants of diabetic mothers (IDM) is known to be higher than in the general population. These malformations usually involve several organ systems and in the past few years there has been an attempt to group them into distinct "syndromes." The present report concerns a child with a specific constellation of findings not yet reported in the infant of a diabetic mother, and we urge our colleagues to look for other associations existing in these infants, rather than just listing series of individual malformations.

Thumb duplication and contralateral thumb hypoplasia in infant of mother with diabetes

Uncontrolled maternal diabetes frequently results in congenital anomalies. This report describes an infant of a mother with diabetes born with thumb hypoplasia and contralateral thumb duplication without other associated anomalies. Maternal diabetes should be part of the etiologic differential diagnosis of thumb anomalies. The concomitant occurrence of thumb duplication and hypoplasia, apparently as a result of the same systemic insult, suggests a close relationship between hypoplasia and duplication.

Atypical postaxial acrofacial dysostosis (AFD): diabetic embryopathy or a new AFD syndrome?

We report on a Brazilian girl, born to a diabetic mother, and presenting with atypical pre/postaxial acrofacial dysostosis, nosologically related to the Genée-Wiedemann syndrome. Clinical and genetic aspects of this acrofacial dysostosis and its relationship to diabetic embryopathy are discussed.

A reappraisal of the CHARGE association

We describe 14 boys and six girls, including monozygotic twins, with the CHARGE association. All of the children had at least four of the seven major features included in the mnemonic CHARGE and all had ear anomalies or deafness or both and either coloboma or choanal atresia or both. All the boys had evidence of hypogonadism. A characteristic facial appearance (unusually shaped ears, unilateral facial palsy, square face, malar flattening, pinched nostrils) was observed in many of our cases. The aetiology remains unknown. All our cases are sporadic.

Oculoauriculovertebral anomaly: variability and causal heterogeneity

The oculoauriculovertebral anomaly is a complex developmental field defect. There is lack of agreement on the minimal diagnostic criteria and the phenotypic spectrum. Causal heterogeneity has been described. This report reviews aspects of phenotypic variability and causal heterogeneity and discusses current understanding of the defect.

Hyperglycemia-induced teratogenesis is mediated by a functional deficiency of arachidonic acid

Congenital malformations now represent the largest single cause of mortality in the infant of the diabetic mother. The mechanism by which diabetes exerts its teratogenic effects is not known. This study evaluated whether arachidonic acid might be involved, a possibility raised by the role of arachidonic acid in palatal elevation and fusion, processes analogous to neural tube folding and fusion. This hypothesis was tested in two animal models of diabetic embryopathy, the in vivo pregnant diabetic rat and the in vitro hyperglycemic mouse embryo culture. The subcutaneous injection of arachidonic acid (200-400 mg/kg per day) into pregnant diabetic rats during the period of organ differentiation (days 6-12) did not alter the maternal glucose concentration, the maternal weight gain, or the weight of the embryos. However, the incidence of neural tube fusion defects was reduced from 11% to 3.8% (P less than 0.005), the frequency of cleft palate was reduced from 11% to 4% (P less than 0.005), and the incidence of micrognathia was reduced from 7% to 0.8% (P less than 0.001). The addition of arachidonic acid to B10.A mouse embryos in culture also resulted in a reversal of hyperglycemia-induced teratogenesis. The teratogenic effect of D-glucose (8 mg/ml) in the medium resulted in normal neural tube fusion in only 32% of the embryos (P less than 0.006 when compared to controls). Arachidonic acid supplementation (1 or 10 micrograms/ml) produced a rate of neural tube fusion (67%) that was not significantly different from that observed in controls. The evidence presented indicates that arachidonic acid supplementation exerts a significant protective effect against the teratogenic action of hyperglycemia in both in vivo (rat) and in vitro (mouse) animal models. These data therefore suggest that the mechanism mediating the teratogenic effect of an increased glucose concentration involves a functional deficiency of arachidonic acid at a critical stage of organogenesis.

Congenital malformations in diabetic pregnancy: the clinical relevance of experimental animal studies

The aim of this work was to present recent observations on the occurrence of malformations in the offspring of diabetic rats and to discuss these findings in the light of present clinical experience. Comparison of malformation rates between different substrains of Sprague-Dawley rats showed marked differences in the occurrence of diabetes-induced malformations. These findings suggest that congenital malformations in diabetic pregnancy may result from a teratological insult in genetically predisposed individuals. Recent clinical reports seem to link facial malformations to an increased incidence of sacral-caudal malformations in human diabetic pregnancy. The present rat model, which expresses both these aberrations--micrognathia and sacral dysgenesis--may therefore be a useful tool in studies of the aetiological relationships between disturbed maternal metabolism and skeletal malformations in the offspring. Malformations in fetuses of diabetic animals seem to arise from teratogenic insult(s) early in pregnancy. Hyperglycemia and hyperketonemia may both singly, and in combination, be of teratological significance. Insulin itself does not appear to be directly teratogenic. Furthermore, there is evidence to suggest that disturbed levels of trace metals, primarily zinc, may be a significant factor in the production of congenital malformations. The increased rate of malformations in diabetic pregnancy, therefore, appears to be multifactorial in origin.

Caudal dysplasia and femoral hypoplasia-unusual facies syndrome: different manifestations of the same disorder?

The Caudal Dysplasia syndrome and the Femoral Hypoplasia-Unusual Facies syndrome have been reported to be more frequent among infants of diabetic mothers. We report a newborn girl who presented with features compatible with both syndromes. The possibility that both conditions represent different manifestations of the same disorder is discussed.