The syndrome of multisynostotic osteodysgenesis with long-bone fractures

Neonatal fractures as a presenting feature of LMOD3-associated congenital myopathy

Nemaline myopathy is a rare inherited disorder characterized by weakness, hypotonia, and depressed deep tendon reflexes. It is clinically and genetically heterogeneous, with the most severe phenotype presenting as perinatal akinesia, severe muscle weakness, feeding difficulties and respiratory failure, leading to early mortality. Pathogenic variants in 12 genes, encoding components of the sarcomere or factors related to myogenesis, have been reported in patients affected with the disorder. Here, we describe an early, lethal presentation of decreased fetal movements, hypotonia, muscle weakness, and neonatal respiratory failure requiring ventilator support in three siblings from a consanguineous family. All exhibited perinatal fractures, and thus, a skeletal dysplasia was considered as possibly contributing to the phenotype. However, whole exome sequencing revealed a homozygous, loss-of-function pathogenic variant in LMOD3, which has recently been associated with nemaline myopathy and, in a subset of patients, perinatal fractures. This case demonstrates the importance of considering congenital neuromuscular disorders in the differential diagnosis of perinatal fractures.

P450 Oxidoreductase deficiency: Analysis of mutations and polymorphisms

Cytochrome P450 oxidoreductase (POR) is required for metabolic reactions of steroid and drug metabolizing cytochrome P450 proteins located in endoplasmic reticulum. Mutations in POR cause a complex set of disorders resembling combined deficiencies of multiple steroid metabolizing enzymes. The P450 oxidoreductase deficiency (PORD) was first reported in patients with symptoms of defects in steroidogenic cytochrome P450 enzymes and ambiguous genitalia, and bone malformation features resembling Antley-Bixler syndrome. POR is now classified as a separate and rare form of congenital adrenal hyperplasia (CAH), which may cause disorder of sexual development (DSD). Since the initial description of PORD in 2004, a large number of POR mutations and polymorphisms have been described. In this report we have performed computational analysis of mutations and polymorphisms in POR linked to metabolism of steroids and xenobiotics and pathology of PORD from the reported cases. The mutations in POR that were identified in patients with disruption of steroidogenesis also have severe effects on cytochrome P450 proteins involved in metabolism of drugs. Different variations in POR show a range of diverse effects on different partner proteins that are often linked to the location of the particular variants. The variations in POR that cause defective binding of co-factors always have damaging effects on all partner proteins, while the mutations causing subtle structural changes may lead to altered interaction with partner proteins and the overall effect may be different for each individual partner. Computational analysis of available sequencing data and mutation analysis shows that Japanese (R457H), Caucasian (A287P) and Turkish (399-401) populations can be linked to unique founder mutations. Other mutations identified so far were identified as rare alleles or in single isolated reports. The common polymorphism of POR is the variant A503V which can be found in about 27% of alleles in general population but there are remarkable differences among different sub populations.

Sonographic Diagnosis of Antley-Bixler PORD-Type Syndrome

Antley-Bixler syndrome (ABS)—consisting of ABS type 1 (skeletal only) and ABS type 2, associated with cytochrome 450 mutations and P450 oxidoreductase deficiency (PORD-ABS)—is a heterogeneous syndrome with a constellation of skeletal deformation findings that classically include skull, facial, and appendicular defects. The hallmarks of ABS type 1 include craniosynostosis, midface hypoplasia, radiohumeral/radioulnar synostosis, arachnodactyly, bowing of the femur, congenital fractures, and choanal atresia. ABS has historically been identified at newborn or childhood examination using radiographic, computed tomography, or stillbirth autopsy. However, in recent years, antenatal ultrasonography has identified craniosynostotic conditions in utero. We present a case of PORD with the ABS phenotype diagnosed by sonography in utero at an early gestation (13–16 weeks), which included mutations in the POR gene. Sonographers, sonologists, and perinatologists aware of the diversity of this rare condition will be well prepared to raise the suspicion of Antley-Bixler PORD-type syndrome.

NADPH P450 oxidoreductase: structure, function, and pathology of diseases

Cytochrome P450 oxidoreductase (POR) is an enzyme that is essential for multiple metabolic processes, chiefly among them are reactions catalyzed by cytochrome P450 proteins for metabolism of steroid hormones, drugs and xenobiotics. Mutations in POR cause a complex set of disorders that often resemble defects in steroid metabolizing enzymes 17α-hydroxylase, 21-hydroxylase and aromatase. Since our initial reports of POR mutations in 2004, more than 200 different mutations and polymorphisms in POR gene have been identified. Several missense variations in POR have been tested for their effect on activities of multiple steroid and drug metabolizing P450 proteins. Mutations in POR may have variable effects on different P450 partner proteins depending on the location of the mutation. The POR mutations that disrupt the binding of co-factors have negative impact on all partner proteins, while mutations causing subtle structural changes may lead to altered interaction with specific partner proteins and the overall effect may be different for each partner. This review summarizes the recent discoveries related to mutations and polymorphisms in POR and discusses these mutations in the context of historical developments in the discovery and characterization of POR as an electron transfer protein. The review is focused on the structural, enzymatic and clinical implications of the mutations linked to newly identified disorders in humans, now categorized as POR deficiency.

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.

Cytochromes P450—A Family of Proteins and Scientists–Understanding their Relationships

The unifying thread of this review involves NADPH-cytochrome P450 reductase (CYPOR), the microsomal enzyme responsible for transferring electrons to cytochromes P450, as well as several other monooxygenase systems, a lifelong interest of the corresponding author. The intersection of her research with that of Dr. David Kupfer, their resulting collaboration, and the beginning of a long-standing study of fatty acid- and eicosanoid-metabolizing cytochromes P450 (CYP4A gene subfamily), including the role of cytochrome b5, will be reported. The culmination of this interest now involves purification and characterization of the human mutants of CYPOR that have been implicated in pathologies, such as Antley-Bixler syndrome.

Foot anomalies in Antley-Bixler syndrome: three case reports

Multiple joint contractures, including radiohumeral synostosis, are the hallmark of Antley-Bixler syndrome (ABS). The detailed description of the skeletal aberration, however, focused in feet is scarce. We carried out the scrutiny for foot lesion in three ABS patients with POR (nicotinamide adenine dinucleotide phosphate-oxidase-cytochrome P450 oxidoreductase) gene mutations, one of whom had undergone surgical intervention for difficulty in walking. Radiographs in all three patients showed middle cuneiform-second metatarsal synostosis and the fourth brachymetapody, irrespective of the severity of their systemic manifestations. In addition, talocalcaneal synostosis, lateral cuneiform-cuboid synostosis, defects of middle phalanx, and distal phalanx-middle phalanx synostosis were found in at least two patients. In conclusion, we found distinctive constellations of foot abnormalities in the patients of ABS with POR gene mutation, which may be useful in planning the treatment strategy, as well as in the diagnostic process.

Apparent manifesting heterozygosity in P450 oxidoreductase deficiency and its effect on coexisting 21-hydroxylase deficiency

CONTEXT

P450 oxidoreductase (POR) deficiency is a disorder of steroidogenesis affecting the microsomal P450 enzymes that use POR as an electron donor. The clinical presentation is variable; patients can be asymptomatic or can present with genital anomalies and the Antley-Bixler syndrome, characterized by craniosynostosis and other bony anomalies. Obligately heterozygous parents are normal. Combined POR and 21-hydroxylase deficiencies have not been reported.

OBJECTIVE

The aim was to explore the manifestations of combined deficiencies of 21-hydroxylase and POR and to search for lesions in apparent manifesting POR heterozygotes.

PATIENTS AND METHODS

A newborn female had craniosynostosis, severe salt wasting, minimal virilization, grossly elevated 17OH-progesterone, and minimally elevated androgens. DNA encoding 21-hydroxylase, POR, and fibroblast growth factor receptor 2 was sequenced. For POR, the first untranslated exon (exon 1U), 5' flanking DNA, and most introns were sequenced in five apparent manifesting POR heterozygotes.

RESULTS

CYP21B mutations were found on both alleles, proving classical 21-hydroxylase deficiency. Fibroblast growth factor receptor 2 exons 8 and 10 were normal. A POR mutation, A287P, was found only on the maternal allele. Five previously reported patients had POR mutations found on only one allele, but their clinical characteristics were indistinguishable from patients with mutations on both alleles. Sequencing of exon 1U, 274 bp of POR 5' flanking DNA, and 12 of the 15 POR introns did not identify additional mutations affecting gene expression or splicing.

CONCLUSION

Manifesting heterozygosity is a possible feature of POR deficiency and may ameliorate the findings in coexisting 21-hydroxylase deficiency.

P450 oxidoreductase deficiency: a new form of congenital adrenal hyperplasia

PURPOSE OF REVIEW

P450 oxidoreductase deficiency--a newly described form of congenital adrenal hyperplasia--typically presents a steroid profile suggesting combined deficiencies of steroid 21-hydroxylase and 17alpha-hydroxylase/17,20-lyase activities. These and other enzymes require electron donation from P450 oxidoreductase. The clinical spectrum of P450 oxidoreductase deficiency ranges from severely affected children with ambiguous genitalia, adrenal insufficiency and the Antley-Bixler skeletal malformation syndrome to mildly affected individuals with polycystic ovary syndrome. We review current knowledge of P450 oxidoreductase deficiency and its broader implications.

RECENT FINDINGS

Since the first report in 2004, at least 21 P450 oxidoreductase mutations have been reported in over 40 patients. The often subtle manifestations of P450 oxidoreductase deficiency suggest it may be relatively common. P450 oxidoreductase deficiency, with or without Antley-Bixler syndrome, is autosomal recessive, whereas Antley-Bixler syndrome without disordered steroidogenesis is caused by autosomal dominant fibroblast growth factor receptor 2 mutations. In-vitro assays of P450 oxidoreductase missense mutations based on P450 oxidoreductase-supported P450c17 activities provide excellent genotype/phenotype correlations. The causal connection between P450 oxidoreductase deficiency and disordered bone formation remains unclear.

SUMMARY

P450 oxidoreductase mutations cause combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase. Individuals with an Antley-Bixler syndrome-like phenotype presenting with sexual ambiguity or other abnormalities in steroidogenesis should be analyzed for P450 oxidoreductase deficiency.

Diversity and function of mutations in p450 oxidoreductase in patients with Antley-Bixler syndrome and disordered steroidogenesis

P450 oxidoreductase (POR) is the obligatory flavoprotein intermediate that transfers electrons from reduced nicotinamide adenine dinucleotide phosphate (NADPH) to all microsomal cytochrome P450 enzymes. Although mouse Por gene ablation causes embryonic lethality, POR missense mutations cause disordered steroidogenesis, ambiguous genitalia, and Antley-Bixler syndrome (ABS), which has also been attributed to fibroblast growth factor receptor 2 (FGFR2) mutations. We sequenced the POR gene and FGFR2 exons 8 and 10 in 32 individuals with ABS and/or hormonal findings that suggested POR deficiency. POR and FGFR2 mutations segregated completely. Fifteen patients carried POR mutations on both alleles, 4 carried mutations on only one allele, 10 carried FGFR2 or FGFR3 mutations, and 3 patients carried no mutations. The 34 affected POR alleles included 10 with A287P (all from whites) and 7 with R457H (four Japanese, one African, two whites); 17 of the 34 alleles carried 16 "private" mutations, including 9 missense and 7 frameshift mutations. These 11 missense mutations, plus 10 others found in databases or reported elsewhere, were recreated by site-directed mutagenesis and were assessed by four assays: reduction of cytochrome c, oxidation of NADPH, support of 17alpha-hydroxylase activity, and support of 17,20 lyase using human P450c17. Assays that were based on cytochrome c, which is not a physiologic substrate for POR, correlated poorly with clinical phenotype, but assays that were based on POR's support of catalysis by P450c17--the enzyme most closely associated with the hormonal phenotype--provided an excellent genotype/phenotype correlation. Our large survey of patients with ABS shows that individuals with an ABS-like phenotype and normal steroidogenesis have FGFR mutations, whereas those with ambiguous genitalia and disordered steroidogenesis should be recognized as having a distinct new disease: POR deficiency.

A child with Saethre-Chotzen syndrome, sensorineural hearing loss, and a TWIST mutation

OBJECTIVE

Patients with syndromic craniosynostosis may have associated hearing deficits. A review of hearing loss associated with syndromic craniosynostosis as well as implications of cochlear implantation in the craniosynostosis patients is presented. In the literature, patients with Saethre-Chotzen syndrome have been shown to have conductive or mixed hearing losses. This case report describes a patient with Saethre-Chotzen syndrome caused by a mutation in the TWIST gene who exhibits a severe to profound sensorineural hearing loss.

Evidence for digenic inheritance in some cases of Antley-Bixler syndrome?

The Antley-Bixler syndrome has been thought to be caused by an autosomal recessive gene. However, patients with this phenotype have been reported with a new dominant mutation at the FGFR2 locus as well as in the offspring of mothers taking the antifungal agent fluconazole during early pregnancy. In addition to the craniosynostosis and joint ankylosis which are the clinical hallmarks of the condition, many patients, especially females, have genital abnormalities. We now report abnormalities of steroid biogenesis in seven of 16 patients with an Antley-Bixler phenotype. Additionally, we identify FGFR2 mutations in seven of these 16 patients, including one patient with abnormal steroidogenesis. These findings, suggesting that some cases of Antley-Bixler syndrome are the outcome of two distinct genetic events, allow a hypothesis to be formulated under which we may explain all the differing and seemingly contradictory circumstances in which the Antley-Bixler phenotype has been recognised.

Antley-Bixler syndrome: a disorder characterized by congenital synostosis of the elbow joint and the cranial suture

The Antley-Bixler syndrome is a rare disorder characterized by craniosynostosis, midface hypoplasia, radiohumeral synostosis, joint contractures, arachnodactyly, and femoral bowing and fractures. We report four cases with this disorder, all of which had craniosynostosis, midface hypoplasia with characteristic facial appearance, and contractures of bilateral elbow joints. However, femoral bowing, fractures, and arachnodactyly were not seen in our patients. In addition, proximal phalanges of the thumb and the great toe showed deformity of the delta phalanx in two cases. Characteristic features in these cases were the synostotic deformity of the elbow joint; three had radioulnahumeral synostosis, and one had radioulnar synostosis. Therefore, our cases indicated that various synostotic patterns of the elbow joints may exist in this syndrome. It is reasonable to propose that characteristic craniofacial appearance associated with the synostosis of the elbow joints of various forms should be considered minimal diagnostic criteria of the Antley-Bixler syndrome.

The Antley-Bixler syndrome: report of two familial cases with severe renal and anal anomalies

The Antley-Bixler syndrome is characterized by premature closure of coronal and lambdoidal sutures, proptosis, depression of the nasal bridge, brachycephaly, radio-humeral synostosis and bowing of ulnae and femora associated with fractures. Most cases have been reported after birth with only one case diagnosed prenatally after recurrence of this autosomal recessive syndrome. The two present cases are of interest because of prenatal diagnosis of renal agenesis in the first case and early detection of clinical signs during the second pregnancy. Beside the unusual severity of the renal abnormalities, both cases had an imperforate anus in addition to the more common genital abnormalities.

CONCLUSION

Renal agenesis and imperforate anus may occur in the Antley-Bixler syndrome.

Antley-Bixler syndrome and esophageal atresia in a patient with trisomy 21

The Antley-Bixler syndrome (ABS) is characterized by craniofacial, skeletal and urogenital anomalies. While most patients with ABS die of severe respiratory complications in their first months, long-term survivors have been reported. We report an infant girl, born to a consanguineous couple, with craniofacial and skeletal anomalies, consistent with ABS, in addition to atresia of the esophagus and trisomy 21.

Antley-Bixler syndrome: report of a patient and review of literature

We report a patient with Antley-Bixler syndrome and review 13 patients from the literature. The cardinal features of this condition include craniosynostosis, severe mid-face hypoplasia, proptosis, choanal atresia/stenosis, frontal bossing, dysplastic ears, depressed nasal bridge, radiohumeral synostosis, long-bone fractures and femoral bowing, urogenital abnormalities and a normal karyotype. Early death was identified in 54% of the reported cases, usually due to respiratory complications. The oldest patient at the time of follow up was 10 years of age. Intellectual performance has been variable (developmental testing of our patient at 30 months of age showed a range of developmental skills equivalent to 6 to 11 months of age). Chronic respiratory distress, especially if accompanied by periods of apnea, may be important in the causation of mental retardation. Some patients with the syndrome have normal intelligence, which suggests a normally developing brain, particularly if a craniectomy is performed to treat sutural synostosis and indicates that there may be secondary factors (e.g., apnea) playing a role in the mental retardation (as seen in our patient with a history of apnea) in patients with the Antley-Bixler syndrome. Since choanal atresia/stenosis which diminishes the airway passage is a cardinal feature of this syndrome, choanal stenting should be performed on those patients with this finding during infancy to decrease the airway obstruction. All patients followed beyond infancy were ambulatory, including our patient at 35 months of age, who will take steps with assistance. Although most cases are sporadic, there were reports of recurrence in siblings of both sexes in two families, suggesting an autosomal recessive mode of inheritance.

Antley-Bixler syndrome: description of two patients

The Antley-Bixler syndrome comprises malformations of cartilage and bone. The essential signs are a dysmorphic facies with flattening of the central region of the face, humeroradial synostosis with flexed attitude of the upper limbs and swelling of the distal interphalangeal and metacarpophalangeal articulations. Congenital atresia of the nasal choanae, which is often present, makes the prognosis of this syndrome extremely severe. Two patients affected by the syndrome are described. Atresia of the nasal choanae was absent in both. The first patient had genital ambiguity, a condition which has been described in the literature in only two other cases; the second one had all the fundamental characteristics of the syndrome except for humeroradial synostosis, although hypoplasia of the lateral condyle of the humerus and dislocation of the radius are present in association with synostosis between the 2nd metatarsal and the intermediate cuneiform.

Humero-radial synostosis with ulnar defects in sibs

Sibs with virtually identical humero-radial synostosis (HRS) are presented and compared with 17 previously reported cases from the literature of recessively transmitted HRS. The range of anomalies described includes (in addition to humero-radial synostosis) ulnar hypoplasia, patellar hypoplasia, and chronic glomerulo-nephritis.

Antley-Bixler syndrome from a prognostic perspective: report of a case and review of the literature

The Antley-Bixler syndrome (ABS) is characterized by craniosynostosis, radiohumeral synostosis, and femoral bowing. Other findings include a trapezoid-shaped head, deformed ears, severe midface hypoplasia, choanal atresia or stenosis, and long bone fractures. Most ABS cases have died in the first months of life from respiratory complications. The poor prognosis in this condition makes counseling difficult and early termination of pregnancy a consideration. The medical and surgical management information presented here can be used as a guide for counseling parents in the future. We report on a new patient with ABS who now at age 3 yr, has been followed by the medical staff of Riley Children's Hospital since birth. She has had successful medical and surgical management. Although the multisynostoses seen in this disorder is undoubtedly related to the soft tissue malformations such as choanal stenosis and midface hypoplasia, the cause remains unknown. The literature is also reviewed in this condition.

Bone fragility, craniosynostosis, ocular proptosis, hydrocephalus, and distinctive facial features: a newly recognized type of osteogenesis imperfecta

We report two infants with bone deformities and multiple fractures reminiscent of osteogenesis imperfecta, but also having ocular proptosis with orbital craniosynostosis, hydrocephalus, and distinctive facial features. Both infants were normal at birth, but multiple compression fractures of the long bones were noted shortly thereafter, followed by extensive demineralization and culminating in recurrent diaphyseal fractures of the weight-bearing bones before the first birthday. The striking similarity of both the distinctive dysmorphic features and the unique pattern of fractures in two unrelated individuals suggests that this is a previously unrecognized form of osteogenesis imperfecta. Despite the craniosynostosis and hydrocephalus, intellectual performance is unimpaired in both individuals. Bone biopsy in one patient revealed decreased bone volume and increased bone resorption without compensatory new bone formation. Extensive laboratory investigations have not identified a cause, nor have they clarified pathogenesis; further elucidation will require the identification and study of new cases.

Multisynostotic osteodysgenesis

A sporadic case of multisynostotic osteodysgenesis is reported in a 15-day-old female infant with urogenital abnormalities. The main radiological findings were craniosynostosis, radiohumeral synostosis, femoral bowing and fractures. The typical combination of clinical and radiologic findings allow the ready recognition of this syndrome. Seven earlier cases have been reported, five sporadic and one familial; in two sisters.

A new syndrome with camptodactyly, joint contractures, facial anomalies, and skeletal defects: a case report and review of syndromes with camptodactyly

A new camptodactyly syndrome is described in a 16-year-old Sephardic Jewish girl consisting of unusual facies with multiple eye anomalies, short stature, scoliosis, and joint contractures. Parental consanguinity is suggestive of an autosomal recessive mode of inheritance, although a new autosomal dominant mutation cannot be excluded. Fourty-four syndromes associated with camptodactyly are summarized and reviewed.

Antley-Bixler syndrome in sisters: a term newborn and a prenatally diagnosed fetus

Sisters with the Antley-Bixler syndrome are reported herein. The first infant died at 14 days of respiratory failure and the following findings characteristic of the syndrome: craniosynostosis of coronal and lambdoid sutures, brachycephaly, frontal bossing, severe midface hypoplasia with proptosis and choanal stenosis/atresia, humero-radial synostosis, medial bowing of ulnae, long slender fingers with camptodactyly, narrow iliac wings, anterior bowing of femora, cardiac and renal malformations. Unlike two previously published cases, she did not have connatal fractures, but she had vaginal atresia. Ultrasound examination in a subsequent pregnancy showed immobility at the elbows of the fetus, humero-radial synostosis, medial bowing of ulnae, and long hands and fingers. The fetus also had mild bowing of femora. The pregnancy was terminated in the 21st week and the findings were confirmed by clinical and radiologic examinations. Additional autopsy findings included cardiac and renal malformations. The Antley-Bixler syndrome is a recognizable malformation syndrome with a probable autosomal recessive mode of inheritance, which can be diagnosed in the fetus by midtrimester ultrasound examination.

The Antley-Bixler syndrome

Three unrelated children (two girls and one boy) with the Antley-Bixler syndrome have been evaluated, bringing to five the number of patients reported with this disorder. All have had brachycephaly, midface hypoplasia, dysplastic ears, radiohumeral synostosis, and joint contractures. Craniosynostosis has been documented radiographically in four of the five patients. All five have had a severely shortened cranial base. Femoral bowing with neonatal fractures has been a variable feature. All have represented sporadic occurrences in otherwise normal families.

Prenatal ultrasound detection of humero-radial synostosis in a case of Antley-Bixler syndrome

The Antley-Bixler syndrome is characterized by multiple skeletal fusions including humero-radial synostosis, anterior bowing of the femora, cardiac and renal malformations and a high incidence of early postnatal lethality. In the pregnancy of a mother who had previously given birth to a child with the Antley-Bixler syndrome, prenatal ultrasound diagnosis was performed at 17 and 20 weeks. Fixed flexion of about 80 degrees in both elbows was seen together with humero-radial synostosis and bowing of the ulnae. The fetus performed jerky craniocaudal movements in its shoulders, but did not, during five hours of real-time observation, move at all in the elbows. Mild anterior bowing of the femora was also observed. The pregnancy was terminated at 21 weeks, and radiological examination of the female fetus confirmed the above mentioned findings including complete bilateral humero-radial synostosis. She also had cardiac and renal malformations. An ultrasound diagnosis of syndromes which have humero-radial synostosis as one feature is possible. Immobility and flexion in the elbows during a long period is probably the essential diagnostic finding.