Antley-Bixler syndrome, description of two new cases and review of the literature

Differential diagnosis of syndromic craniosynostosis: a case series

Purpose

Syndromic craniosynostosis is a rare genetic disease caused by premature fusion of one or multiple cranial sutures combined with malformations of other organs. The aim of this publication is to investigate sonographic signs of different syndromic craniosynostoses and associated malformations to facilitate a precise and early diagnosis.

Methods

We identified in the period of 2000–2019 thirteen cases with a prenatal suspected diagnosis of syndromic craniosynostosis at our department. We analyzed the ultrasound findings, MRI scans, genetic results as well as the mode of delivery, and postnatal procedures.

Results

Eight children were diagnosed with Apert Syndrome, two with Saethre Chotzen syndrome, one with Crouzon syndrome, and one with Greig cephalopolysyndactyly syndrome. One child had a mutation p.(Pro253Leu) in the FGFR2 gene. We identified characteristic changes of the head shape as well as typical associated malformations.

Conclusion

Second trimester diagnosis of syndromic craniosynostosis is feasible based on the identified sonographic signs. In case of a suspected diagnosis a genetic, neonatal as well as surgical counseling is recommended. We also recommend to offer a fetal MRI. The delivery should be planned in a perinatal center.

Ultrasound and MR imaging findings in prenatal diagnosis of craniosynostosis syndromes

BACKGROUND

Craniosynostosis syndromes are uncommonly encountered in the prenatal period. Identification is challenging but important for family counseling and perinatal management.

OBJECTIVE

This series examines prenatal findings in craniosynostosis syndromes, comparing the complementary roles of US and MRI and emphasizing clues easily missed in the second trimester.

MATERIALS AND METHODS

Six prenatal cases evaluated from 2002 through 2011 were retrospectively reviewed. Referral history, gestational age, and sonographic and MRI findings were reviewed by three pediatric radiologists. Abnormalities of the calvarium, hands, feet, face, airway and central nervous system were compared between modalities.

RESULTS

The diagnosis was Apert syndrome in three, Pfeiffer syndrome in two and Carpenter syndrome in one. The gestational age at evaluation ranged from 21 to 33 weeks. All six were evaluated by MRI and US, with two undergoing repeat evaluation in the third trimester, yielding a total of eight MRIs and US exams. The referral history suggested cloverleaf skull in two cases but did not suggest craniosynostosis syndrome in any case. In four, the referral suggested central nervous system (CNS) findings that were not confirmed by MRI; additional CNS findings were discovered in the remaining two. In four cases, developing turricephaly resulted in a characteristic "lampshade" contour of the fetal head. Hypertelorism and proptosis were present in five, with proptosis better appreciated by MRI. Digit abnormalities were present in all, seen equally well by MRI and US. Lung abnormalities in the second trimester in one fetus resolved by the third trimester.

CONCLUSION

Prenatal diagnosis of craniosynostosis syndromes is difficult prior to the third trimester. MRI and US have complementary roles in evaluation of these patients.

FGFR2 mutation in 46,XY sex reversal with craniosynostosis

Patients with 46,XY gonadal dysgenesis (GD) exhibit genital anomalies, which range from hypospadias to complete male-to-female sex reversal. However, a molecular diagnosis is made in only 30% of cases. Heterozygous mutations in the human FGFR2 gene cause various craniosynostosis syndromes including Crouzon and Pfeiffer, but testicular defects were not reported. Here, we describe a patient whose features we would suggest represent a new FGFR2-related syndrome, craniosynostosis with XY male-to-female sex reversal or CSR. The craniosynostosis patient was chromosomally XY, but presented as a phenotypic female due to complete GD. DNA sequencing identified the FGFR2c heterozygous missense mutation, c.1025G>C (p.Cys342Ser). Substitution of Cys342 by Ser or other amino acids (Arg/Phe/Try/Tyr) has been previously reported in Crouzon and Pfeiffer syndrome. We show that the 'knock-in' Crouzon mouse model Fgfr2c(C342Y/C342Y) carrying a Cys342Tyr substitution displays XY gonadal sex reversal with variable expressivity. We also show that despite FGFR2c-Cys342Tyr being widely considered a gain-of-function mutation, Cys342Tyr substitution in the gonad leads to loss of function, as demonstrated by sex reversal in Fgfr2c(C342Y/-) mice carrying the knock-in allele on a null background. The rarity of our patient suggests the influence of modifier genes which exacerbated the testicular phenotype. Indeed, patient whole exome analysis revealed several potential modifiers expressed in Sertoli cells at the time of testis determination in mice. In summary, this study identifies the first FGFR2 mutation in a 46,XY GD patient. We conclude that, in certain rare genetic contexts, maintaining normal levels of FGFR2 signaling is important for human testis determination.

Gross Motor Function of a Child With Antley-Bixler Syndrome

BACKGROUND AND PURPOSE

Antley-Bixler syndrome (ABS) is an exceptionally rare genetic disorder presenting multiple malformations of bone requiring extensive medical and surgical management for survival. Current literature focuses on medical and surgical care without an emphasis on (re)habilitation. This case report describes the physical therapy (PT) care of a child with particularly complex ABS.

CASE DESCRIPTION

The child was a 3-year-old girl with ABS with a significant developmental delay. She received PT between the ages of 12 and 36 months within a specialized long-term care facility.

OUTCOMES

After treatment, she demonstrated change in her ability to assume and maintain developmental positions as noted during annual examinations. The standardized assessment tool used failed to capture change in functional abilities.

DISCUSSION

Further research was recommended to guide clinical reasoning and determine effectiveness of PT for children with ABS.

VIDEO ABSTRACT

For more insights from the author, access Supplemental Digital Content 1, available at: http://links.lww.com/PPT/A86.

Spectrum of Antley-Bixler syndrome

Antley-Bixler syndrome (ABS) is an exceptionally rare craniosynostosis syndrome characterized by radiohumeral synostosis present from the perinatal period. There is a wide spectrum of anomalies seen within ABS, and other features include midface hypoplasia; choanal stenosis or atresia; multiple joint contractures; visceral anomalies, particularly of the genitourinary system; and impaired steroidogenesis. The condition of ABS is curious in that mutations of 2 separate genes have been identified and that there seem to be subtle phenotypic differences between the 2 genotypes. Mutations of the P450 oxidoreductase gene have been reported in those patients with genital anomalies and/or impaired steroidogenesis, and the S351C mutation of the fibroblast growth factor receptor 2 gene has been reported predominantly in those patients with normal genitalia and steroidogenesis. We report a series of 4 patients with ABS and review their main findings and management.

Otologic findings in Antley-Bixler syndrome: a clinical and radiologic case report

Antley-Bixler syndrome (ABS) is characterized by craniofacial dysmorphism and radiohumeral synostosis with other associated anomalies. Prior studies have commonly described the entirety of the syndrome or the genetic abnormalities underlying the syndrome, however, no study has specifically addressed the otologic findings of ABS. We present a case of ABS, specifically focusing on the otologic ramifications of the disease, and provide recommendations for approaching the otologic management of these complex patients.

Hydrocephalus in craniosynostosis: a review

INTRODUCTION

Ventricular dilatation in the presence of primary craniosynostosis is a unique condition with respect to pathogenesis, clinical significance, and morphological appearance. It is rarely observed in nonsyndromic craniosynostosis, and in these cases usually attributable to coincidental disorders. Conversely, it is a common feature of syndromic craniosynostosis, affecting at least 40% of patients with Crouzon's, Pfeiffer's or the Apert syndrome. Shunt-dependent hydrocephalus is predominantly associated with Crouzon or Pfeiffer syndrome while in the Apert syndrome the usual finding is nonprogressive ventriculomegaly which, however, may also occur in some cases of Crouzon syndrome.

PATHOGENESIS

The pathogenesis of progressive hydrocephalus remains somewhat obscure, a hypoplastic posterior fossa and a venous outlet occlusion at the skull base being the main causative factors discussed in literature. Ventriculomegaly may reflect primary brain maldevelopment or in some cases even a compensated state of increased cerebrospinal fluid (CSF) outflow resistance. CLINICAL EVALUATION: Clinical evaluation is mainly aimed at identifying progressive hydrocephalus, but diagnosis is hampered by the fact that classical clinical signs may be absent, and that ventricular dilatation will often become evident only after decompressive cranial surgery. Moreover, mild ventriculomegaly may in some cases coexist with intracranial hypertension from craniostenosis. Therefore, careful monitoring of intracranial pressure and ventricular size in the pre- and postoperative period is a diagnostic mainstay.

CONCLUSION

In true hydrocephalus ventriculo-peritoneal shunting is currently the single promising mode of treatment.

Chiari malformation in craniosynostosis

INTRODUCTION

Chiari malformation (CM) is a frequent finding in multisutural and syndromic craniosynostosis, occurring in 70% of patients with Crouzon's syndrome, 75% with oxycephaly, 50% with Pfeiffer's syndrome and 100% with the Kleeblattschädel deformity. The pathogenesis of this condition and rationale for treatment are still controversial.

DISCUSSION

Since its first description in 1972, several factors have been cited to play a role in inducing CM. In the light of recent publications, the roles of premature fusion of cranial vault and cranial base sutures, of congenital anomalies of the cerebellum and brain stem, of raised intracranial pressure, of venous hypertension and of hydrocephalus are reviewed. Evaluation and management of CM are also discussed.

CONCLUSION

Chiari malformation appears to be an acquired and progressive condition that develops in the first months of life, because of a disproportion between hindbrain growth and an abnormally small posterior fossa, a consequence of the premature fusion of lambdoid and cranial base sutures. Venous hypertension caused by stenosis of the jugular foramen can also be present in these patients, resulting in intracranial hypertension and/or hydrocephalus. Careful MRI evaluation is recommended for the forms of craniosynostosis at a high risk of developing hindbrain herniation. The selection of posterior cranial vault expansion as the first surgical procedure is advocated. In selected cases, treatment of the posterior cranial deformity by occipital vault remodelling and treatment of the Chiari-like deformity by suboccipital decompression can be carried out using the same surgical procedure.

Correction of facial deformity using a Red III device in a patient with Antley-Bixler syndrome

Antley-Bixler syndrome was first described in 1975 and to date at least 44 cases have been reported. In addition to brachycephaly, this syndrome is associated with midface hypoplasia, bilateral radiohumeral synostosis, multiple joint contractures, long bone fractures, dysplastic ears, "pear shaped" nose, and occasionally urogenital or cardiac defects. The authors report a case in a 23-year-old man with severe midface deficiency treated using distraction osteogenesis. A modified Le Fort III osteotomy was performed, and nasal subunit and remaining Le Fort III segment was distracted separately. The classic RED II design was found to be insufficient, so the authors added an extra horizontal bar to the system and converted it to a RED III design. Midface advancement was 11 mm from the porion to the orbitale and 31 mm at point A. Nasal advancement at the nasal root level was 5 mm. There were no complications, and at 4 months after surgery, advancement was stable without any relapse.

A male twin infant with skull deformity and elevated neonatal 17-hydroxyprogesterone: a prismatic case of P450 oxidoreductase deficiency

We report on a male twin infant who presented with brachy-turri-cephaly, frontal bossing, large anterior fontanelle, low set and malformed ears, and mild arachnodactyly. He had normal male genitalia. There was no evidence for maternal virilization during pregnancy. The pattern of malformations resembled Antley-Bixler-Syndrome (ABS). However, sequencing analysis of the fibroblast growth factor receptor 2 gene (FGFR2) did not reveal mutations. The boy's twin sister did not show any somatic or endocrine abnormalities. In the boy, neonatal screening for congenital adrenal hyperplasia was positive with moderately elevated 17-hydroxyprogesterone. Sequence analysis of his CYP21 gene did not reveal any mutations. The short synacthen test revealed an exaggerated 17-hydroxyprogesterone and a blunted cortisol response. Urinary steroid profiling by gas chromatography-mass spectrometry (GC-MS) revealed a unique steroid metabolome suggestive of impaired activity of both 17-hydroxylase and 21-hydroxylase. Clinical and metabolic findings therefore were compatible with the recently described variant of congenital adrenal hyperplasia, P450 oxidoreductase deficiency (ORD). Subsequently, sequencing analysis of CPR, the gene encoding P450 oxidoreductase (OR), revealed a homozygous mutation in the patient, resulting in an amino acid exchange in position 284 of the OR protein (A284P). Both the female twin sister and the parents were heterozygous for the A284P mutation. P450 oxidoreductase deficiency represents a novel autosomal recessively inherited form of congenital adrenal hyperplasia. Its characteristic steroid metabolome can readily be detected by GC-MS analysis of spot urine. Clinical features may include an ABS phenotype, ambiguous genitalia (virilization in girls, feminization in boys), and glucocorticoid deficiency. If required, hydrocortisone replacement should be provided.

Abnormal steroidogenesis in three patients with Antley-Bixler syndrome: apparent decreased activity of 17alpha-hydroxylase, 17,20-lyase and 21-hydroxylase

BACKGROUND

Antley-Bixler syndrome (ABS) is characterized mainly by abnormal skeletal morphogenesis such as craniosynostosis and radiohumeral synostosis, and by ambiguous genitalia in some cases. The mechanisms resulting in these deformities have not been determined.

METHODS

The adrenal and gonadal function of three Japanese ABS patients were evaluated. Patient 1 (17-year-old-male) had bilateral cryptoorchidism, delayed puberty and symptoms of glucocorticoid deficiency. Patient 2 (14-year-old male) and patient 3 (4-year-old female) presented with emaciation. Additionally, patient 3 had partial labial fusion and common urogenital sinus. In each patient, blood sampling for steroid analysis before and after rapid adrenocorticotropic hormone (ACTH) stimulation was carried out. Additionally, urinary steroids were quantified. Molecular analysis of CYP17 and CYP21A2 were also performed.

RESULTS

All patients showed elevated basal 17alpha-deoxysteroid levels. Although the 17alpha-deoxysteroid levels further increased after rapid ACTH stimulation, 17alpha-hydroxysteroids including cortisol did not respond, suggesting impaired 17alpha-hydroxylation. Patient 1 and patient 2 showed low adrenal androgen blood levels both before and after rapid ACTH stimulation. Patient 3 showed lower than normal excretions of urinary androgens. Additionally, a prolonged ACTH stimulation in patient 3 failed to elicit significant increase of adrenal androgens. These findings suggested impaired 17,20-lyase activity. In contrast to attenuated 17alpha-hydroxycorticosteroids, notably cortisol, elevated 17alpha-hydroxyprogesterone (17OHP) levels were observed, not only in pubertal patients (1 and 2) but also in prepubertal patient 3, indicating impaired 21-hydroxylation. This assumption was supported by increased urinary 21-deoxycortisol metabolite excretion in patients 2 and 3. With the exception of a heterozygous mutation of CYP17 in one of the patients, other mutations of this gene or CYP21A2 were identified in any of the patients.

CONCLUSION

Combined decreased 17alpha-hydroxylation, 17,20-lyase activity and 21-hydroxylation was detected in three ABS patients. Considering that the enzymes responsible are all cytochrome P450 enzymes and that another cytochrome P450 enzyme, lanosterol 14alpha-demethylase, has recently been shown to be impaired in an ABS patient, we speculate that dysfunction of a system which commonly regulates cytochrome P 450 activity may be responsible for the ABS phenotype.

Compound heterozygous mutations of cytochrome P450 oxidoreductase gene (POR) in two patients with Antley-Bixler syndrome

Antley-Bixler syndrome (ABS) is characterized by skeletal defects including craniosynostosis and radiohumeral synostosis. Although mutations in the FGFR2 gene have been found in some patients called ABS, genetic heterogeneity of this syndrome has been proposed. We have previously reported three ABS patients with unique abnormalities in steroidogenesis (apparent decreased activity of 17alpha-hydroxylase, 17,20-lyase, and 21-hydroxylase). Decreased activity of lanosterol 14alpha-demethylase has also been described in an ABS patient. Since all these enzymes require cytochrome P450 oxidoreductase (encoded by POR) as an electron donor, we studied POR in two unrelated ABS patients with abnormal steroidogenesis. Direct sequencing of POR revealed that both patients had compound heterozygous mutations (1329insC and R454H in a male patient, 1698insC and R454H in a female patient). The two insertional mutations were assumed to generate truncated and unstable mRNAs. The R454H mutation was assumed to be deleterious because the R454 resides in the FAD-binding domain and is highly conserved among diverse species. Our results demonstrate that mutations in POR cause the ABS phenotype with autosomal recessive inheritance and with characteristic abnormalities in steroidogenesis.

Reoperation for Chiari malformations

BACKGROUND

We undertook this study to characterize those patients who required reoperations for Chiari malformation and to determine whether modifications in surgical technique at the initial procedure might have obviated the need for repeat surgery.

METHODS

We reviewed the hospital records, imaging studies, operative reports, and follow-up data of those patients who were undergoing a second operation as part of a consecutive series of Chiari decompressions carried out by one neurosurgeon over a 14-year period. We wished to determine whether type of Chiari malformation, age at initial surgery, the presence of associated bony anomalies, or initial operative technique contributed to the need for reoperation.

RESULTS

Twenty-two (17%) of the surgical procedures represented reoperations (16 of 100 Chiari I and 6 of 33 Chiari II decompressions). Of the patients in the series who were operated on at age 5 years or younger, 7 (16%) were reoperations (5 of 33 Chiari I and 2 of 10 Chiari II decompressions); 15 patients (17%) of those older than 5 years at surgery were reoperations (11 of 67 Chiari I and 4 of 23 Chiari II decompressions). 8 of the 16 patients who underwent reoperations for Chiari I malformation and 4 of the 6 patients who underwent reoperations for Chiari II malformation had their initial decompression surgery at age 5 years or younger. Reoperation was required because of failure to treat adequately an associated syrinx (n=11), because of persisting neurological symptoms or headache (n=9), or because of a possible faulty fourth ventricular stent placement (n=2). 5 of 9 patients in the operative series with Chiari malformations associated with craniosynostosis represented reoperations (55%), and all 3 of the patients whose syrinx persisted after reoperation had craniosynostosis syndromes.

CONCLUSIONS

Approximately 17% of the patients with Chiari I and Chiari II malformations in this operative series were undergoing a second operation. Factors in this series which were associated with reoperation included a young age at initial surgery, the presence of complex bony anatomy at the foramen magnum, syndromic craniosynostosis, and failure of the surgeon at the initial operation either to assess patency of the foramen of Magendie or correctly place a fourth ventricular stent.