The acrocallosal syndrome

Prenatal diagnosis of a severe form of frontonasal dysplasia with severe limb anomalies, hydrocephaly, a hypoplastic corpus callosum, and a ventricular septal defect using 3D ultrasound: a case report and literature review

BACKGROUND

Frontonasal dysplasia (FND) is a rare congenital anomaly resulting from the underdevelopment of the frontonasal process, and it can be syndromic or nonsyndromic. The typical features of FND include a deformed nose and ocular hypertelorism, which are sometimes associated with cleft lip and/or palate. Only approximately 10 cases of prenatally diagnosed nonsyndromic FND have been reported in the past 30 years.

CASE PRESENTATION

A 33-year-old woman (G2P1) was referred to our center at 20 gestational weeks for bilateral hydrocephaly. We detected typical features of FND, including severe hypertelorism, median nasal bifidity, a minor cleft lip, and multiple limb anomalies using three-dimensional (3D) ultrasound. A hypoplastic corpus callosum, unilateral microtia, and a ventricular septal defect were also detected. Genetic testing, including karyotype analysis, copy number variation (CNV) analysis, trio-whole exome sequencing (trio-WES), and trio-whole-gene sequencing (trio-WGS), was performed; however, we did not find any de novo gene variants in the fetus as compared to the parents. Postmortem examination confirmed the prenatal diagnosis of FND.

CONCLUSION

The present case expands the wide phenotypic spectrum of prenatal FND patients. 3D ultrasound is a useful tool for detecting facial and limb deformities.

Gli3 controls the onset of cortical neurogenesis by regulating the radial glial cell cycle through Cdk6 expression

The cerebral cortex contains an enormous number of neurons, allowing it to perform highly complex neural tasks. Understanding how these neurons develop at the correct time and place and in accurate numbers constitutes a major challenge. Here, we demonstrate a novel role for Gli3, a key regulator of cortical development, in cortical neurogenesis. We show that the onset of neuron formation is delayed in Gli3 conditional mouse mutants. Gene expression profiling and cell cycle measurements indicate that shortening of the G1 and S phases in radial glial cells precedes this delay. Reduced G1 length correlates with an upregulation of the cyclin-dependent kinase gene Cdk6, which is directly regulated by Gli3. Moreover, pharmacological interference with Cdk6 function rescues the delayed neurogenesis in Gli3 mutant embryos. Overall, our data indicate that Gli3 controls the onset of cortical neurogenesis by determining the levels of Cdk6 expression, thereby regulating neuronal output and cortical size.

The many faces of KIF7

Mutations in KIF7, the gene that encodes a component of the kinesin complex of anterograde intraflagellar transport in the cilia, have been reported to cause a range of phenotypes including hydrolethalis, acrocallosal syndrome and Joubert syndrome. In a cohort of patients with various neurogenetic phenotypes, we identified novel KIF7 mutations in two families that span the known phenotypic spectrum of KIF7-related disorders. Surprisingly, we also identified a novel truncating KIF7 mutation in a third consanguineous family, in which the index presented with intellectual disability but no overt signs of ciliopathy, and his brain magnetic resonance imaging revealed an isolated dysgenesis of corpus callosum. This small cohort contributes novel pathogenic alleles of KIF7 and suggests that KIF7-related phenotypes can include isolated dysgenesis of corpus callosum with intellectual disability, thus expanding the range of phenotypes that warrant sequencing of this gene.

A de novo GLI3 mutation in a patient with acrocallosal syndrome

Acrocallosal syndrome is characterized by postaxial polydactyly, macrocephaly, agenesis of the corpus callosum, and severe developmental delay. In a few patients with this disorder, a mutation in the KIF7 gene has been reported, which was associated with impaired GLI3 processing and dysregulaton of GLI3 transcription factors. A single patient with acrocallosal syndrome and a de novo p.Ala934Pro mutation in GLI3 has been reported, whereas diverse and numerous GLI3 mutations have also been described in syndromes with overlapping clinical manifestations, including Greig cephalopolysyndactyly syndrome, Pallister-Hall syndrome, trigonocephaly with craniosynostosis and polydactyly, oral-facial-digital syndrome, and non-syndromic polydactyly. Here, we describe a second patient with acrocallosal syndrome, who has a de novo, novel c.2786T>C mutation in GLI3, which predicts p.Leu929Pro. This mutation is in the same domain as the mutation in the previously reported patient. These data confirm that mutations in GLI3 are a cause of the acrocallosal phenotype.

Sibs with anencephaly, anophthalmia, clefts, omphalocele, and polydactyly: hydrolethalus or acrocallosal syndrome?

Major characteristics of the acrocallosal syndrome include severe mental retardation, agenesis or hypoplasia of the corpus callosum, and polydactyly of fingers and toes. In the past few years, anencephaly has also been noted, together with other midline defects. We report on a nonconsanguineous, Norwegian couple with a history of two pregnancies with a male and a female fetus, respectively, with anencephaly, median cleft lip and palate, omphalocele, and preaxial polydactyly, suggesting the diagnosis of the acrocallosal syndrome. Both fetuses also lacked eyes and nose, a finding not previously reported in the acrocallosal syndrome. Microphthalmia has been reported in the hydrolethalus syndrome, which may be caused by mutations in the same gene as the acrocallosal syndrome. The present report adds support to the hypothesis that the acrocallosal and hydrolethalus syndromes may be allelic conditions. The family history is consistent with autosomal recessive inheritance.

Acrocallosal syndrome: a case report

This report describes the case of an 18-month-old Caucasian male infant with clinical and radiological findings indicative of the Schinzel acrocallosal syndrome. He was born to non-consangiuneous parents. His father had been diagnosed with Greig syndrome. The patient underwent surgery for preaxial polysyndactyly of both hands and feet. The similarity to the Greig syndrome is discussed. It is possible that both the acrocallosal syndrome and the Greig syndrome are variant expressions of the same autosomal dominant condition. Surgery may improve thumb opposition and shoe wear.

Acrocallosal syndrome in an Algerian boy born to consanguineous parents: review of the literature and further delineation of the syndrome

We present a 17-month-old boy with the acrocallosal syndrome. He was born to consanguineous parents. Abnormal findings included agenesis of the corpus callosum, a ventricular septal defect (VSD), postaxial polydactyly of fingers, cleft soft palate, intestinal malrotation, large anterior fontanelle, prominent forehead, hypertelorism, epicanthic folds, short nose and mandible and preauricular skin tags, mixed hearing loss, laryngomalacia, and growth and severe motor and mental retardation. A review of previous reports on the acrocallosal syndrome shows considerable clinical variability; minimal diagnostic criteria are proposed. A developmental field defect with disturbance of midline development is suggested.

Molecular genetic approaches to the study of human craniofacial dysmorphologies

Craniofacial dysmorphologies are common, ranging from simple facial disfigurement to complex malformations involving the whole head. With the advent of gene mapping and cloning techniques, the genetic element of both simple and complex human craniofacial dysmorphologies can be investigated. For many of the dysmorphic syndromes, it is possible to find families that display a particular phenotype in either an autosomal dominant, recessive, or X-linked manner. This article focuses on a subgroup of craniofacial dysmorphologies, covering these three main inheritance patterns, that are being studied using molecular biology techniques: DiGeorge syndrome, Treacher Collins syndrome, Greig cephalopolysyndactyly syndrome, acrocallosal syndrome, amelogenesis imperfecta, and X-linked cleft palate with ankyloglossia. Once the mutated or deleted gene or genes for each syndrome have been cloned, patterns of normal and abnormal craniofacial development should be elucidated. This should enhance both diagnosis and treatment of these common and disfiguring disorders.

Acrocallosal syndrome in two African brothers born to consanguineous parents

We describe two mentally retarded brothers with craniofacial anomalies, polydactyly, and other clinical manifestations compatible with the acrocallosal syndrome (ACS). These are the first black patients from Africa with this diagnosis. They are also the fourth set of sibs described with ACS, and together with the parental consanguinity documented in this family, confirm autosomal recessive inheritance of this syndrome. The clinical manifestations in our patients confirm the intrafamilial variability of the syndrome. Postnatal onset of growth retardation is proposed as an additional manifestation of ACS.

Fronto-nasal dysostosis, callosal agenesis, crossed-fused ectopia, tibial hemimelia, and preaxial polydactyly of feet: severe expression of the acrocallosal syndrome?

We report on a girl with frontonasal "dysostosis," callosal agenesis, crossed-fused ectopia, tibial hemimelia, and preaxial polydactyly of feet. This pattern of the developmental defects suggests a severe form of the acrocallosal syndrome. Implications for genetic counselling are discussed.

The acrocallosal syndrome and Greig syndrome are not allelic disorders

Acrocallosal syndrome is an autosomal recessive form of polysyndactyly associated with mental retardation and agenesis of the corpus callosum. There have been suggestions that it is allelic to the Greig cephalopolysyndactyly syndrome. Linkage analysis, using flanking markers, shows this suggestion is unlikely to be correct.

A family with one child with acrocallosal syndrome, one child with anencephaly-polydactyly, and parental consanguinity

A 2-year-old boy with typical features of the acrocallosal syndrome is presented. His parents are first degree cousins and their first pregnancy resulted in spontaneous abortion whereas the offspring of their second pregnancy was an anencephalic baby with bilateral post-axial polydactyly of the hands. The possibility of including anencephaly in the spectrum of the CNS malformations of the acrocallosal syndrome is suggested.

Further delineation of the acrocallosal syndrome

The acrocallosal syndrome (ACS) was recognized by Schinzel in 1979 as a specific entity, characterized by the association of craniofacial anomalies, total or partial agenesis of corpus callosum, polysyndactyly and mental retardation. The inheritance is autosomal recessive, based on instances of recurrence in siblings and cousins and parental consanguinity. A large inbred kindred with recurrent ACS is presented. This family further strengthens the hypothesis of autosomal recessive inheritance for this syndrome. The array of clinical manifestations in this sibship and those previously reported exemplify the phenomenon of inter- and intrafamilial variability that must be considered when defining ACS. Based on a review of published reports and the present family, essential, additional and occasional findings are distinguished. Attention is drawn to geographical clustering of the families.

Holoprosencephaly-polydactyly ('pseudotrisomy 13') syndrome: a syndrome with features of hydrolethalus and Smith-Lemli-Opitz syndromes. A collaborative multicentre study

A syndrome of holoprosencephaly and postaxial polydactyly, associated with hydrocephalus, heart defect, adrenal hypoplasia, and other visceral malformations, has been observed in five unrelated children with normal chromosomes. Clinical overlap with lethal acrodysgenital dwarfism (Smith-Lemli-Opitz syndrome type II) and hydrolethalus syndrome is discussed. Recessive inheritance seems likely.

How wide is the clinical spectrum of the acrocallosal syndrome? Report of a mild case

A boy presenting with an incomplete form of the acrocallosal syndrome is described. The syndrome shows clinical variability and it is stressed that none of the components is constant and facial dysmorphism is not always characteristic.

Acrocallosal syndrome

Acrocallosal syndrome is an autosomal recessive disorder of brain malformation and complex polydactyly. We report on an additional patient with this disorder. It is suggested that increased birth weight and cerebellar hypoplasia occur in acrocallosal syndrome. The finding of an extra bone within the anterior fontanel in our patient suggests similarity to the Xt mouse mutant, which is homologous to Greig syndrome in man. This provides additional support for the hypothesis of allelism of the Greig and acrocallosal syndromes.

The acrocallosal syndrome in a Turkish boy

A 6 month old Turkish boy with the acrocallosal syndrome is reported. The patient, born to consanguineous, healthy parents, presented with macrocephaly, a prominent forehead, hypertelorism, polydactyly of the fingers and toes, severe motor and mental retardation, hypotonia, and absence of the corpus callosum. The mode of inheritance is discussed and our case is compared with previously reported cases of the syndrome.

Acrocallosal syndrome: additional manifestations

The acrocallosal syndrome (ACS) is a probable autosomal recessive condition of macrocephaly, craniofacial and hand and foot abnormalities, absence of the corpus callosum, and mental retardation. This patient had characteristics of the ACS but also had a severe congenital heart defect and other visceral malformations. After comparing the ACS with and contrasting it to other disorders, we concluded that the internal organ abnormalities found in this patient probably represent further manifestations of the ACS.

Acrocallosal syndrome: new findings

We describe a 21-month-old girl with typical manifestations of the acrocallosal syndrome of craniofacial anomalies, agenesis of the corpus callosum, hallucal duplication, severe hypotonia, and psychomotor retardation. Our patient also had the Dandy-Walker malformation, imperforate anus with rectovaginal fistula, hypothalamic dysfunction with hypothyroidism and diabetes insipidus, thick, dysplastic pulmonic valve leaflets, central and obstructive apnea, and pulmonary hypertension. These findings add to the delineation of this syndrome.