Frontonasal dysplasia, coronal craniosynostosis, pre- and postaxial polydactyly and split nails: a new autosomal dominant mutant with reduced penetrance and variable expression?

Severe craniofrontonasal syndrome in a male patient mosaic for a novel nonsense mutation in EFNB1

Craniofrontonasal syndrome (CFNS) is an X-linked disorder caused by mutations in EFNB1. Uncommonly and paradoxically, female patients with CFNS exhibit significantly more severe symptoms than male patients. This is explained by "cellular interference". Nevertheless, there have been a few reports of male patients severely affected with CFNS due to postzygotic mosaicism. Here, we demonstrated a male patient with severe CFNS. Whole exome sequencing showed that he harbored both wild type and nonsense mutation, c.253C > T (p.Gln85Ter), in the EFNB1 gene. Sanger sequencing of his leukocytes, buccal swab, and hair root revealed a variable level of mosaicism. This nonsense mutation is absent in his parents and has never been previously reported. Our findings expand the mutational spectrum of EFNB1 and substantiates that males with severely affected CFNS are mosaic.

Aberrant cell segregation in the craniofacial primordium and the emergence of facial dysmorphology in craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS) is a rare X-linked disorder characterized by craniofacial, skeletal, and neurological anomalies and is caused by mutations in EFNB1. Heterozygous females are more severely affected by CFNS than hemizygous males, a phenomenon called cellular interference that results from EPHRIN-B1 mosaicism. In Efnb1 heterozygous mice, mosaicism for EPHRIN-B1 results in cell sorting and more severe phenotypes than Efnb1 hemizygous males, but how craniofacial dysmorphology arises from cell segregation is unknown and CFNS etiology therefore remains poorly understood. Here, we couple geometric morphometric techniques with temporal and spatial interrogation of embryonic cell segregation in mouse mutant models to elucidate mechanisms underlying CFNS pathogenesis. By generating EPHRIN-B1 mosaicism at different developmental timepoints and in specific cell populations, we find that EPHRIN-B1 regulates cell segregation independently in early neural development and later in craniofacial development, correlating with the emergence of quantitative differences in face shape. Whereas specific craniofacial shape changes are qualitatively similar in Efnb1 heterozygous and hemizygous mutant embryos, heterozygous embryos are quantitatively more severely affected, indicating that Efnb1 mosaicism exacerbates loss of function phenotypes rather than having a neomorphic effect. Notably, neural tissue-specific disruption of Efnb1 does not appear to contribute to CFNS craniofacial dysmorphology, but its disruption within neural crest cell-derived mesenchyme results in phenotypes very similar to widespread loss. EPHRIN-B1 can bind and signal with EPHB1, EPHB2, and EPHB3 receptor tyrosine kinases, but the signaling partner(s) relevant to CFNS are unknown. Geometric morphometric analysis of an allelic series of Ephb1; Ephb2; Ephb3 mutant embryos indicates that EPHB2 and EPHB3 are key receptors mediating Efnb1 hemizygous-like phenotypes, but the complete loss of EPHB1-3 does not fully recapitulate the severity of CFNS-like Efnb1 heterozygosity. Finally, by generating Efnb1+/Δ; Ephb1; Ephb2; Ephb3 quadruple knockout mice, we determine how modulating cumulative receptor activity influences cell segregation in craniofacial development and find that while EPHB2 and EPHB3 play an important role in craniofacial cell segregation, EPHB1 is more important for cell segregation in the brain; surprisingly, complete loss of EPHB1-EPHB3 does not completely abrogate cell segregation. Together, these data advance our understanding of the etiology and signaling interactions underlying CFNS dysmorphology.

Tooth Abnormalities and Occlusal Disorders in Individuals with Frontonasal Dysplasia

Objective

Frontonasal dysplasia is a rare developmental defect of the midface, and little is known about the dental involvement in individuals with this condition. This study investigated tooth abnormalities and occlusal disorders in individuals with frontonasal dysplasia.

Design

Cross-sectional.

Setting

Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo, Bauru, Brazil.

Interventions

Clinical oral examination, analysis of patient records, and panoramic radiographs.

Participants

A total of 20 individuals with frontonasal dysplasia aged 7 to 17 years.

Main Outcome Measures

Prevalence of the several tooth abnormalities and occlusal disorders analyzed.

Results

A total of 19 individuals presented at least one tooth abnormality, with highly variable findings. In radiographs, 20% of individuals (all presenting oral clefts) presented agenesis of lateral incisors and second premolars. No supernumerary teeth were observed; 65% of individuals exhibited occlusal alterations, especially anterior open bite in the two individuals with median cleft lip.

Conclusions

Variable clinical and radiographic alterations were observed, probably due to the large variety of phenotypic characteristics. No specific dental alteration could be related with frontonasal dysplasia.

A novel ciliopathic skull defect arising from excess neural crest

The skull is essential for protecting the brain from damage, and birth defects involving disorganization of skull bones are common. However, the developmental trajectories and molecular etiologies by which many craniofacial phenotypes arise remain poorly understood. Here, we report a novel skull defect in ciliopathic Fuz mutant mice in which only a single bone pair encases the forebrain, instead of the usual paired frontal and parietal bones. Through genetic lineage analysis, we show that this defect stems from a massive expansion of the neural crest-derived frontal bone. This expansion occurs at the expense of the mesodermally-derived parietal bones, which are either severely reduced or absent. A similar, though less severe, phenotype was observed in Gli3 mutant mice, consistent with a role for Gli3 in cilia-mediated signaling. Excess crest has also been shown to drive defective palate morphogenesis in ciliopathic mice, and that defect is ameliorated by reduction of Fgf8 gene dosage. Strikingly, skull defects in Fuz mutant mice are also rescued by loss of one allele of fgf8, suggesting a potential route to therapy. In sum, this work is significant for revealing a novel skull defect with a previously un-described developmental etiology and for suggesting a common developmental origin for skull and palate defects in ciliopathies.

Isolated Sagittal Synostosis in a Boy with Craniofrontonasal Dysplasia and a Novel EFNB1 Mutation

Craniofrontonasal syndrome (CFNS) is a rare X-linked disorder that shows greater severity in females and is largely attributed to mutations in EFNB1. A 7-year-old boy presented with hypertelorism, broad nasal root, midfacial hypoplasia, mandibular prognathia, ptosis, and scaphocephaly was clinically diagnosed with CFNS. Three-dimensional computed tomographic scans confirmed the isolated sagittal synostosis. His mother also showed clinical features of CFNS, but less severe. Genetic tests uncovered a novel C to T mutation at nucleotide 466 (c.466C>T) in exon 1 of EFNB1 for both. To the best of our knowledge, this is the only reported incident of CFNS in a male child exhibiting isolated sagittal synostosis.

Phenotypes of craniofrontonasal syndrome in patients with a pathogenic mutation in EFNB1

Craniofrontonasal syndrome (CFNS) is an X-linked developmental malformation, caused by mutations in the EFNB1 gene, which have only been described since 2004. A genotype-phenotype correlation seems not to be present. As it is of major importance to adequately counsel patients with EFNB1 mutations and their parents, and to improve diagnosis of new patients, more information about the phenotypic features is needed. This study included 23 patients (2 male, 21 female) with confirmed EFNB1 mutations. All patients underwent a thorough physical examination and photographs were taken. If available, radiological images were also consulted. Hypertelorism, longitudinal ridging and/or splitting of nails, a (mild) webbed neck and a clinodactyly of one or more toes were the only consistent features observed in all patients. Frequently observed phenotypic features were bifid tip of the nose (91%), columellar indentation (91%) and low implantation of breasts (90%). In comparison with anthropometric data of facial proportions, patients with CFNS had a significantly different face in multiple respects. An overview of all phenotypic features is shown. Patients with EFNB1 mutations have a clear phenotype. This study will facilitate genetic counseling of parents and patients, and contribute to the diagnostic and screening process of patients with suspected CFNS.

Cellular interference in craniofrontonasal syndrome: males mosaic for mutations in the X-linked EFNB1 gene are more severely affected than true hemizygotes

Craniofrontonasal syndrome (CFNS), an X-linked disorder caused by loss-of-function mutations of EFNB1, exhibits a paradoxical sex reversal in phenotypic severity: females characteristically have frontonasal dysplasia, craniosynostosis and additional minor malformations, but males are usually more mildly affected with hypertelorism as the only feature. X-inactivation is proposed to explain the more severe outcome in heterozygous females, as this leads to functional mosaicism for cells with differing expression of EPHRIN-B1, generating abnormal tissue boundaries—a process that cannot occur in hemizygous males. Apparently challenging this model, males occasionally present with a more severe female-like CFNS phenotype. We hypothesized that such individuals might be mosaic for EFNB1 mutations and investigated this possibility in multiple tissue samples from six sporadically presenting males. Using denaturing high performance liquid chromatography, massively parallel sequencing and multiplex-ligation-dependent probe amplification (MLPA) to increase sensitivity above standard dideoxy sequencing, we identified mosaic mutations of EFNB1 in all cases, comprising three missense changes, two gene deletions and a novel point mutation within the 5′ untranslated region (UTR). Quantification by Pyrosequencing and MLPA demonstrated levels of mutant cells between 15 and 69%. The 5′ UTR variant mutates the stop codon of a small upstream open reading frame that, using a dual-luciferase reporter construct, was demonstrated to exacerbate interference with translation of the wild-type protein. These results demonstrate a more severe outcome in mosaic than in constitutionally deficient males in an X-linked dominant disorder and provide further support for the cellular interference mechanism, normally related to X-inactivation in females.

Misexpression of Six2 is associated with heritable frontonasal dysplasia and renal hypoplasia in 3H1 Br mice

A radiation-induced mouse mutant, Brachyrrhine (Br), exhibits frontonasal dysplasia and renal hypoplasia, two malformations associated with deficiencies in mesenchymal condensation. The purpose of this study was to resolve the Br locus, evaluate possible candidate genes, and identify developmental defects in the mutant chondrocranium. Linkage analysis mapped the Br mutation to a critical region distal to D17Mit76, which contains only one gene, the transcription factor Six2. Sequence analysis of the Six2 gene, including 1.5 kb of the promoter, failed to reveal the Br mutation. However, homozygous Br/Br embryos showed almost complete absence of Six2 mRNA and protein in craniofacial and renal tissues while heterozygous Br/+ embryos displayed intermediate Six2 levels. Mutant embryos displayed malformations of neural crest-derived structures of the anterior cranium where Six2 is normally expressed. These data suggest a mutation in a novel cis-acting regulatory region inhibits Six2 expression and is associated with frontonasal dysplasia and renal hypoplasia.

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.

New dental findings in the median cleft facial syndrome

BACKGROUND

The main features of median cleft facial syndrome are hypertelorism, cranium bifidum occultum, widow's peak, and midine clefting of the nose, upper lip and palate. Since this pathology was first described in 1967, many cases have been reported in the literature, but none of these reports has addressed oral anomalies in depth.

CASE DESCRIPTION

The authors present the case of a female patient aged 4 years and 7 months who was diagnosed with median cleft facial syndrome. In this case, the patient had an abnormal number of teeth, owing to fusion or agenesis of teeth, supernumerary teeth and ectopic eruption of some teeth. These oral anomalies had not been described before in the literature as being associated with this syndrome.

CLINICAL IMPLICATIONS

Median cleft facial syndrome is a rare pathology; however, dentists should know its possible alterations at an oral level, because children with this syndrome need dental treatment to achieve good esthetics and correct occlusion.

The syndrome of frontonasal dysplasia, spastic paraplegia, mental retardation and blindness: a case report with CT scan findings and review of literature

Frontonasal dysplasia is defined as hypertelorism, telecanthus and broad bridge of the nose with absent or bifid tip of the nose. The clinical, the CT scan and the operative findings of a case of frontonasal dysplasia with spastic paraplegia, mental retardation, blindness, and cleft lip and cleft palate are discussed. The contemporary literatures on this rare congenital anomaly are also reviewed.

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.

Craniofrontonasal syndrome: study of 41 patients

Of 41 patients with craniofrontonasal syndrome, 35 were female and 6 were male. Although most cases were sporadic, 7 familial instances were found. Craniofrontonasal syndrome represents a unique, incompletely understood X-linked disorder. Unusual manifestations in females included thick, wiry, and curly hair (49%), anterior cranium bifidum (6%), axillary pterygia (9%), unilateral breast hypoplasia (postpubertal; 11%), and asymmetric lower limb shortness (14%).

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.

Frontonasal and craniofrontonasal dysplasia: preoperative quantitative description of the cranio-orbito-zygomatic region based on computed and conventional tomography

The unoperated crano-orbito-zygomatic complex of 18 children (mean 4.7 years) with frontonasal dysplasia (FND) and 12 children (mean 1.1 years) with crainofrontonasal dysplasia (CFND) was quantified by 15 standard measurements performed on either computed tomography scans or facial tomograms. The results were compared with age-matched control values. In the FND group, the mean anterior interorbital and mid-interorbital distances were significantly increased at 148% and 118% of normal, and in the CFND patients, at 177% and 140% of normal. Excessive medial orbital wall protrusion (mean, 145% of normal in FND and 177% in CFND), shortened zygomatic arch lengths (mean, 94% of normal in FND and 91% in CFND), and reduced cephalic lengths (mean, 96% of normal in FND and 83% in CFND) were all observed. An expanded interzygomatic buttress distance was documented only in the CFND group, at 11% of normal. The clinical presentation of craniofacial deformities such as FND and CFND can be objectively described by a numerical analysis of the bony pathology.

Craniofrontonasal dysplasia

We report on nine patients with craniofrontonasal dysplasia (CFND). Seven classical cases had facial features suggestive of frontonasal dysplasia and coronal craniosynostosis. Extracranial abnormalities such as brittle nails with prominent longitudinal grooves or syndactyly of fingers and toes were observed in individual patients. In two families the father of classical cases showed a milder pattern of abnormalities, consistent with the diagnosis. We present a 2- to 13-year follow-up on our patients. Hypotonia and laxity of joints are common and may necessitate supportive measures. Mild developmental delay was noted in three out of six classical cases studied in detail. Unlike almost all other X-linked disorders, clinical expression in CFND is generally much more severe in females than in males. In contrast to previous reports of this condition, one of our severely affected cases is a male.

Acrocallosal syndrome: report of a Brazilian girl

We report on a Brazilian girl born to nonconsanguineous parents and presenting with frontonasal dysostosis, callosal agenesis, abnormal upper lids, cleft lip/palate, redundant skin in the neck, grooved chin, and bifid thumbs. Major diagnostic criteria present in this patient are related to the acrocallosal syndrome. The clinical and major nosologic aspects of this condition are discussed.

Craniofrontonasal dysostosis: variable expression in a three-generation family

A family with craniofrontonasal dysostosis (craniofrontonasal dysplasia) is described. There were three severely affected females, two of them daughters of apparently healthy parents. Examination of the male relatives revealed orbital hypertelorism and other minor anomalies in two of them, including the father of the two affected daughters. This family emphasizes the wide variation in the phenotype of craniofrontonasal dysostosis and suggests that male relatives with minor manifestations of the syndrome may be at high risk of having severely affected daughters. The expression of the gene may be modified by the sex.

Craniofrontonasal dysostosis with deafness and axillary pterygia

Craniofrontonasal dysostosis (CFND) is an inherited disorder previously referred to as craniofrontonasal dysplasia. However, there is no evidence of tissue dysplasia and, therefore, the term dysostosis has been substituted. The disorder is characterized by frontonasal dysostosis, coronal craniostenosis, and the variable presence of other skeletal defects, including short webbed neck, sloping shoulders, polydactyly, syndactyly, and broad first toes. Here we report an affected mother and daughter who also have limited hip abduction. In addition, the mother had an axillary pterygia, congenital footplate fixation of the left ear, and right sensorineural hearing loss; these manifestations have not been reported previously in CFND and expand the phenotype of this syndrome. Both patients had marked restriction of shoulder abduction, and the mother had limited forearm pronation; these manifestations have been reported in only one other patient with CFND. Awareness of the possibility of these abnormalities may allow for early intervention by physical therapy and hearing aides in infants and young children with these manifestations as a component of CFND.

Autosomal recessive acro-fronto-facio-nasal dysostosis associated with genitourinary anomalies

We report a 6-month-old boy, born of consanguineous (first-cousin) parents (F = 1/16) presenting microbrachycephaly, wide forehead, marked hypertelorism, broad nose with a midline groove with a bilateral small "blind dimple" in each side, hypospadias, syndactyly between fingers 3 and 4, broad thumbs, and halluces. This association of anomalies suggests the diagnosis of a "new" type of acro-fronto-facio-nasal dysostosis. Normal chromosomes, parental consanguinity, and familial occurrence suggest autosomal recessive inheritance.

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.

Greig cephalopolysyndactyly syndrome: a possible mouse homologue (Xt-extra toes)

Greig cephalopolysyndactyly syndrome is an autosomal dominant form of complex polydactyly in man. Attention is called to the evidence that, on both morphological and comparative gene mapping grounds, this defect is homologous to Xt-extra toes in the mouse. The pattern of polydactyly in both species is very similar. In addition, both conditions probably map close to the T-cell receptor gamma polypeptide at 13 A2-3 in mouse and 7p15 in humans.

Chromosomal localisation of a developmental gene in man: direct DNA analysis demonstrates that Greig cephalopolysyndactyly maps to 7p13

Greig cephalopolysyndactyly syndrome (GCPS) is a rare autosomal dominant form of complex polydactyly. GCPS has been tentatively assigned to chromosome 7 on the basis of association of the condition with balanced translocations involving the short arm of chromosome 7 (7p13) in two families. Seven GCPS pedigrees with no chromosome abnormality were studied, and linkage was demonstrated between GCPS and the DNA sequence coding for the receptor for epidermal growth factor (localised to 7p12-13) (Z = 3.17; O = theta).

Frontonasal malformation as a field defect and in syndromic associations

Several new "syndromes" have been described that have in common facial findings identical or similar to those seen in frontonasal malformation (FNM), previously termed frontonasal dysplasia. Some of those new syndromes are inherited, whereas FNM is an isolated finding. Thus there is a need for differentiation among those conditions. A review of the literature was undertaken to identify and classify the various reports that describe FNM as it occurs alone and in association with a syndrome.

Craniofrontonasal dysplasia: phenotypic expression in females and males and genetic considerations

The phenotype and pattern of inheritance of craniofrontonasal dysplasia were analyzed in 66 affected persons from 18 families, including one four-generation kindred personally studied. Females were more severely affected than males. Affected females had hypertelorism, broad nasal root, frontal bossing, craniosynostosis, syndactyly of toes and fingers, and vertical grooving of nails. Males had increased bony interorbital distances and distances between the inner canthi of the eyes, broad nasal root, broad halluces, and vertical grooving of nails but no craniosynostosis. Affected men transmitted the condition to all of their daughters but to no sons, while affected women transmitted the disorder to about half their daughters and half their sons. This pattern is compatible with X-linked dominant inheritance, but the far milder manifestation of the syndrome in males cannot be explained by simple mendelian genetics.

Heterogeneity and variability in the oral-facial-digital syndromes

The oral-facial-digital syndromes are a heterogeneous group of conditions sharing oral, facial, and digital anomalies. Based on more or less subtle clinical differences, at least seven causally different entities can be identified in this group. These include 1) oral-facial-digital syndrome (OFDS) I; 2) Mohr syndrome (OFDS II); 3) OFDS III; 4) OFDS with tibial anomalies (OFDS IV); 5) Thurston syndrome; 6) Varadi syndrome; and 7) Whelan syndrome. However, since differentiation between these entities is based on clinical findings, this classification should be viewed as tentative until more definitive methods are available.

New autosomal dominant syndrome resembling craniofrontonasal dysplasia

Craniofrontonasal dysplasia, a distinct malformation syndrome, is characterized by varying degrees of frontonasal dysplasia, craniosynostosis, and variable extracranial abnormalities--in particular, brittle nails with prominent longitudinal grooves or splitting. There is marked female preponderance and variable expressivity not only between males and females but also between females. However, mode of inheritance is still unclear. We describe a large Arab kindred with 16 individuals (9 males, 7 females) in 4 generations having an apparently new autosomal dominant syndrome with features of craniofrontonasal dysplasia but with normal or slightly broad nasal tip and without evidence of craniosynostosis or nail abnormalities. These cases were segregating in 5 sibships and include male to male transmission with full expression in males and females. Chromosomes of the proposita and her father were normal. Aarskog syndrome has been also considered in the differential diagnosis and was excluded.

A family with craniofrontonasal dysplasia, and fragile site 12q13 segregating independently

Coronal craniosynostosis, hypertelorism, telecanthus, broad grooved nasal tip, dental anomalies, mild syndactyly and broad thumbs, consistent with craniofrontonasal dysplasia are described in a family of four affected females over three generations. Documentation of the family is of interest because of variable clinical features and an excess of affected females. The excess of females observed in this condition is as yet unexplained, but cannot be referred simply to X-linked dominance with lethality in the male. Autosomal dominance with less frequent and less severe expression in the male is more tenable. Chromosome analysis on two affected family members revealed a fragile site at 12q13, which was also found in a phenotypically normal family member. A third affected individual did not exhibit this fragile site. Thus it appears that there is a heritable fragile 12q13 site segregating in this family separately from the gene for craniofrontonasal dysplasia.

Frontonasal "dysplasia," cerebral anomalies, and polydactyly: report of a new syndrome and discussion from a developmental field perspective

We describe a boy with frontonasal "dysplasia"; cerebral anomalies, including agenesis of corpus callosum and probable Dandy-Walker malformation (absent superior vermis, hypoplastic cerebellum and brain stem, and possible posterior fossa cyst in this case); short neck, relatively long trunk with short limbs; cryptorchidism; and polydactyly of hands and feet. We suspect he has a previously undescribed syndrome of presently unknown cause. We also discuss this case from a developmental field perspective, in view of the unusual combination of cerebral and facial defects.