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

Acromelic frontonasal dysostosis and ZSWIM6 mutation: phenotypic spectrum and mosaicism

Acromelic frontonasal dysostosis (AFND) is a distinctive and rare frontonasal malformation that presents in combination with brain and limb abnormalities. A single recurrent heterozygous missense substitution in ZSWIM6, encoding a protein of unknown function, was previously shown to underlie this disorder in four unrelated cases. Here we describe four additional individuals from three families, comprising two sporadic subjects (one of whom had no limb malformation) and a mildly affected female with a severely affected son. In the latter family we demonstrate parental mosaicism through deep sequencing of DNA isolated from a variety of tissues, which each contain different levels of mutation. This has important implications for genetic counselling.

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.

Salvage of calvarial bone graft using acellular dermal matrix in nasal reconstruction and secondary rhinoplasty for frontonasal dysplasia

Frontonasal dysplasia is a severe malformation composed of cranial, ophthalmic, nasal, upper lip, and palatal deformities. Reconstruction in these patients requires complex craniofacial efforts. A 19-year-old woman with frontonasal dysplasia was treated at our institution where she had undergone multiple prior reconstructive surgeries including facial bipartition and cantilevered calvarial bone graft for nasal reconstruction. She later presented with a palpable bone graft prominence, associated contour deformity, and an area of overlying paper-thin skin at the nasal tip. Although there was no ulceration, the threat of graft extrusion required immediate attention. The prominent bone graft tip was debrided, and the overlying soft tissue envelope was augmented using acellular dermal matrix. No surgical complication was encountered. The patient had successful salvage of the bone graft and a pleasing aesthetic outcome at 9 months of follow-up. The use of acellular dermal matrix has proven to be beneficial in the correction of nasal contour deformities given its soft, natural appearance, availability, affordability, and safety. Its use also avoids further donor site morbidity. We suggest acellular dermal matrix as a graft material in revision rhinoplasties for cases of acquired nasal contour deformity and threatened bone graft extrusion. This is the first report known to the authors using acellular dermal matrix during staged nasal reconstruction in a patient experiencing frontonasal dysplasia.

The spectrum of median craniofacial dysplasia

Given the multiple permutations in craniofacial malformations, classification of median craniofacial dysplasia or midline Tessier no. 0 to 14 clefts has been difficult and disjointed. In this review, the authors present a summary of normal embryology, prior terminology, and their proposed new classification system. Median craniofacial dysplasia has tissue agenesis and holoprosencephaly at one end (the hypoplasias), frontonasal hyperplasia and excessive tissue (the hyperplasias) at the other end, and abnormal splitting or clefting and normal tissue volume (dysraphia) occupying the middle portion of the spectrum. These three distinct subclassifications have different forms of anomalies within their groups.

Subtypes of frontonasal dysplasia are useful in determining clinical prognosis

Frontonasal dysplasia [FND; OMIM 136760] results from abnormal morphogenesis of the frontonasal process with disruption of the formation of the facial midline. Craniofacial anomalies in FND include anterior cranium bifidum, ocular hypertelorism, orofacial clefting and notching or clefting of the alae nasi. The majority of FND cases are sporadic and discordance has been demonstrated in monozygotic twin pairs, arguing against a strong inherited component in pathogenesis. However, pedigrees with Mendelian inheritance and non-recurrent chromosome aberrations in FND patients demonstrate that gene mutations or cytogenetic imbalance can also be important in the etiology of this phenotype. We classified 101 reported cases of FND from the medical literature and three new cases into seven separate FND phenotypic subtypes in addition to isolated FND. Our aim was to evaluate FND patients for distinct phenotypes within the FND spectrum and to determine the evidence for a genetic etiology in each of the different subtypes. Our analysis showed significant differences in the severity of the accompanying malformations and the rates of learning disabilities in the FND subtypes, although the small patient numbers and method of patient ascertainment may have influenced the data. The results suggest that cases with FND should be evaluated for additional anomalies, as these may help to determine prognosis.

Acrocallosal syndrome in fetus: focus on additional brain abnormalities

Acrocallosal syndrome (ACS) is an autosomal recessive disorder characterized by craniofacial dysmorphism, agenesis or hypoplasia of the corpus callosum, duplication of the phalanges of the hallux, more rarely the thumbs, post-axial polydactyly, syndactyly and severe mental retardation. Here we report the two first descriptions of acrocallosal syndrome in fetus with extensive neuropathological study and provide new data regarding additional brain abnormalities in ACS. The first case was a 25-gestational week male fetus displaying craniofacial and limb abnormalities, with bilateral syndactyly of the fourth and fifth fingers, preaxial polydactyly of the left foot and an inter-frontal extra-bone. The second fetus was a 33-gestational week male fetus. His left hand displayed a broad thumb and 4/5 syndactyly. In both cases, gross examination of the brain showed an absence of corpus callosum associated with interhemispheric cysts. The cerebral cortex in front of the cysts was nodular. Upon microscopic examination, the nodular masses corresponded to large dysplastic areas represented by clusters of undifferentiated neurons in the white matter. The cyst wall showed arachnoidal and ependymal covering and contained numerous choroid plexus, suggesting a developmental abnormality of the ventricles. The pons and the cerebellum were hypoplastic. The dentate nuclei were fragmented. Numerous neuronal heterotopias associated with ectopic ependymal cavities were observed in the vermis in one case. The olivary nuclei were severely dysplastic too. We hope that these new data will make both the ante- and post-natal diagnosis easier, facilitate comparisons with animal models and encourage the identification of the genes responsible for this syndrome.

Holoprosencephaly and limb reduction defects: a consideration of Steinfeld syndrome and related conditions

Individuals with holoprosencephaly (HPE) and limb reduction defects have been ascribed historically to a variety of syndromes with overlapping phenotypic features. As such, these patients are challenges for clinicians and researchers alike. In an effort to better understand this association, we reviewed our autopsy records and identified five cases of HPE with reduction defects of the limbs and other anomalies. One case appears to be the third reported instance of Steinfeld syndrome, while others represent microgastria-limb reduction sequence, VATER/VACTERL association, and an additional unique condition characterized by HPE, rhombencephalosynapsis, absent left radius, first metacarpal, and thumb, and congenital heart disease. The phenotypic heterogeneity inherent in these patients continues to complicate diagnosis, which will hopefully be simplified by continuing delineation at morphologic and especially genetic levels.

Familial acromelic frontonasal dysostosis: autosomal dominant inheritance with reduced penetrance

Acromelic frontonasal dysostosis (AFND) represents a subgroup of patients with frontonasal malformation with limb abnormalities including preaxial polydactyly and tibial hypoplasia. Previous case reports have suggested autosomal recessive inheritance, given parental consanguinity. However, no affected siblings have been described. Longitudinal clinical history is limited as many do not survive the first years of life. The molecular basis of AFND is not known. Previous investigators have proposed that AFND may result from a perturbation in the Sonic Hedgehog pathway. We present clinical and radiographic findings in two unrelated boys, ages 8 and 9 years, with AFND, one of whom has a family history suggesting dominant inheritance. A focused study of genetic marker data and candidate gene mutation analysis in this family is presented.

Spectrum of the acrocallosal syndrome

Acrocallosal syndrome (ACS) is an autosomal recessive condition, characterized by agenesis of the corpus callosum, pre- and postaxial polydactyly, minor craniofacial anomalies, and, in most patients, severe psychomotor retardation. We here report on three patients with ACS demonstrating a spectrum from mild to severe involvement. Two patients had only mild to moderate mental retardation at the age of 2(1/2) and 4 years, respectively, with surprisingly good speech development. The third patient was severely affected and died at age 7 days because of persistent apnea. All three patients had agenesis of the corpus callosum, and large intracranial cysts, which in the third case was confirmed as a large arachnoid cyst at autopsy. Cranial cysts were also seen in 10/34 published cases of ACS. Thus, intracerebral cysts are a common finding in ACS and may serve in differentiating ACS from Greig cephalopolysyndactyly syndrome.

Associated anomalies in individuals with polydactyly

An epidemiological analysis of the association of polydactyly with other congenital anomalies was performed in 5,927 consecutively born polydactyly cases. They were grouped into three categories: duplicated fifth digit, duplicated first digit, and rare polydactylies; also into isolated or associated groups, if other birth defects were or were not observed in the same infant. Associated cases were further subdivided into: combined, if the other defect was a limb defect; syndromic, if a non-limb defect constituted a recognized causal or pathogenetic entity; and MCA, if a non-limb defect did not constitute a recognized entity. In 14.6% of the 5,927 polydactyly cases studied, polydactyly was not the only congenital anomaly. This associated proportion was minimal for postaxial (11.8%), intermediate for preaxial-I (20.0%), and maximal for rare polydactyly (54.9%). Duplication of the fifth toe plus syndactyly of fourth and fifth toes, as well as other syndactylies adjacent to the duplicated digit is the most frequent type. Syndactyly of fourth and fifth toes was also combined with a duplicated fifth finger, suggesting the existence of an arrested or amputated in utero sixth toe. Polydactylies are rarely associated with other congenital anomalies except in recognizable syndromes. When syndromes are excluded, most of the significant positive associations disappear. Trisomy 13, Meckel, and Down syndrome explained 255 of the 338 syndromic polydactyly cases. Down syndrome is strongly associated with first-digit duplication, and negatively associated with postaxial polydactyly. The latter could not be explained by maternal age differences among Black and non-Black case sub-sets.

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.

Frontonasal dysplasia: analysis of 21 cases and literature review

Twenty-one patients with frontonasal dysplasia were studied. A 2:1 male-to-female sex ratio and increased paternal and maternal ages at the time of conception were found. The significance is uncertain because of small sample size and lack of normal mean values for parental age in Brazil. Apparently, our series is the first to report macrocephaly (six cases). Our series also had a high frequency of patients with agenesis of the corpus callosum (12 cases), basal encephalocele (10 cases), lipoma of the corpus callosum (four cases), and mental deficiency (11 cases). Three patients had the combination of agenesis of the corpus callosum, mental deficiency, and micropenis. It is concluded that frontonasal dysplasia is pathogenetically heterogeneous, representing a regional defect which may not be a single developmental field or sequence. Causal genesis includes a dominantly inherited form, dup(2q), and autosomal recessive Shanske syndrome. Of unknown genesis are two subsets of frontonasal dysplasia patients: 1) the combination of agenesis of the corpus callosum, tibial hypoplasia, and hallucal duplication and 2) ophthalmofrontonasal dysplasia or oculoauriculofrontonasal dysplasia with associated ear tags and epibulbar dermoids.

Oculoauriculofrontonasal syndrome: report of another case and review of differential diagnosis

We report a male with features of frontonasal dysplasia, but also with ocular and auricular defects. This child most likely has oculoauriculofrontonasal syndrome, an autosomal recessive syndrome first described in 1981. We also review the literature on this syndrome, and discuss differential diagnosis.