Prenatal diagnosis of Kniest dysplasia with three-dimensional helical computed tomography

Objective.?Fetal three-dimensional helical computed tomography (3D-CT) has attracted attention in the diagnosis of fetal skeletal dysplasias because of limited diagnostic capabilities of standard ultrasonography to delineate the skeleton. Here we report the first instance of diagnosing Kniest dysplasia with 3D-CT.

Methods.?Fetal 3D-CT was performed for a fetus at 28 weeks' gestation after ultrasonography at 24 weeks had shown moderate shortening of the limbs, mild narrow thorax, and polyhydramnios. The imaging parameters were set so as to reduce estimated fetal irradiation dose to 12.39 mGy of the CT dose index volume and 442 of the dose length product.

Results.?Fetal 3D-CT revealed dumbbell-shaped femora and platyspondyly with coronal cleft of the lumbar vertebral body. This warranted a diagnosis of Kniest dysplasia and corresponded well with postnatal radiographic findings. In retrospect, however, spinal deformation was somewhat underestimated due to image smoothing associated with image processing in 3D-CT. Genetic testing for COL2A1 confirmed Kniest dysplasia; i.e., a de novo mutation of A–C transversion at the splice acceptor site of the 3′ end of intron 16.

Conclusions.?The combined use of 3D-CT with ultrasonography is a power tool for the prenatal diagnosis of congenital skeletal dysplasias.     

Short rib polydactyly syndrome type 3 with absence of fibulae (Verma-Naumoff syndrome)

Short rib polydactyly syndrome (SRPS) is a group of skeletal dysplasias manifested by short-limb dwarfism, short ribs with thoracic dysplasia and polydactyly. SRPS is an inherited autosomal-recessive disorder with different prenatal sonographic and postnatal clinical, histological and radiologic findings. SRPS type 1 (Saldino-Noonan) and type 3 (Verma-Naumoff) are very similar and frequently get mixed. In this report, we present a case of SRPS with hydrops, thoracic hypoplasia, short limbs and postaxial polydactyly in a 27-week fetus. The visceral findings in the fetus including the central nervous system were normal. The karyotype was 46XY. The prenatal diagnosis was thought to be type 1 because of the absence of fibulae at ultrasonography. However, postmortem autopsy, histologic, and radiologic findings were reviewed and the diagnosis was type 3 SRPS because of absence of visceral anomalies, presence of fan-shaped iliac bones and short tubular bones with metaphyseal widening. We concluded that detailed ultrasonography performed in the prenatal period is very important in the diagnosis and differential diagnosis of SRPS.     

Prenatal diagnosis of thanatophoric dysplasia in the second trimester: ultrasonography and other diagnostic modalities

Thanatophoric dysplasia is the most common type of neonatal lethal osteochondrodysplasias, with an estimated frequency of nearly of 1 in 20,000 births. It is a disorder characterized by extremely short ribs, tubular bones and macrocephaly. The prenatal diagnosis of thanatophoric dysplasia has been well established by ultrasonography in the second trimester; however it is not always possible to differentiate the thanatophoric dysplasia fetuses from the others with skeletal dysplasias like fibrochondrogenesis or atelosteogenesis by ultrasonography. Recently, mutations in the fibroblast growth factor receptor 3 gene, located on the short arm of chromosome 4 have been identified as a cause of thanatophoric dysplasia. In this article we described the prenatal diagnosis of two fetuses with thanatophoric dysplasia at 18 and 24 weeks of gestation by ultrasonography. Postpartum radiological and histological analysis confirmed our prenatal diagnosis. Our purpose was to remind the differential prenatal diagnosis with other skeletal dysplasias and new prenatal diagnostic modalities.     

Diastrophic dysplasia: a specific prenatal diagnosis by ultrasound

In a pregnant woman without increased genetic risk, the presence of distrophic dysplasia of the fetus was diagnosed sonographically at 31 weeks' gestation and definitively distinguished from other skeletal dysplasias. In all prenatal diagnosis of diastrophic dysplasia reported so far, this autosomal recessive congenital condition had occurred in the family's previous children and this made the diagnoses of fetal diastrophic dysplasia easier. The reported case was diagnosed due to evidence of an extreme shortening of all long bones of the extremities associated with other skeletal deformities which, taken as a whole, are typical of this syndrome: micrognathia, cervical kyphosis, persistent extension limitation in elbow and knee joints, club feet, ulnar diviation of hands, shortened phalanges, and, in particular, abduction of thumbs ('hitchhiker thumbs') and big toes.     

Short rib-polydactyly syndrome type III: comparison of ultrasound, radiology, and pathology findings

Short rib-polydactyly syndrome (SRPS; types I-IV) is an autosomal recessive, lethal skeletal dysplasia characterized by short-limb dysplasia, narrow thorax, and polydactyly. This syndrome is invariable and can be detected by 2-trimester ultrasound. The underlying gene has not been discovered yet. We report a case of SRPS subtype III Verma-Naumoff-Le Marec that was sonographically detected at 20 weeks' gestation and compare prenatal ultrasound with postmortem findings from pathology and radiology. Since the risk of recurrence is 25%, early ultrasound for consecutive pregnancies was advised and performed at 11+6 weeks' gestation in the following pregnancy without any findings. Ultrasound diagnosis in this rare case of SRPS is a valuable tool for identification and early management, since there are no specific biochemical or histopathological markers for this syndrome. Radiological and pathological findings confirmed SRPS type III and assisted in the differential diagnosis of the subtype.     

Prenatal diagnosis and genetic analysis of type I and type II thanatophoric dysplasia

Thanatophoric dysplasia (TD) is one of the most common neonatal lethal skeletal dysplasias. Prenatal sonographic and molecular genetic diagnoses of three cases of TD type I (TD1) and one case of TD type II (TD2) are presented here. Two fetuses of TD1 were characterized by polyhydramnios, macrocephaly, short limbs, a narrow thoracic cage and curved short femora, but without a cloverleaf skull at 27 and 31 weeks' gestation, respectively. The third fetus with TD1 was, however, not associated with macrocephaly, polyhydramnios, chest narrowing and severe femoral bowing on prenatal ultrasound at 18 weeks' gestation. The TD2 fetus was characterized by polyhydramnios, short limbs, a narrow thoracic cage, straight short femora, hydrocephalus and a cloverleaf skull at 24 weeks' gestation. Three-dimensional ultrasound was able to enhance the visualization of thickened, redundant skin folds and craniofacial and limb deformities associated with TD. Molecular analysis of the fibroblast growth factor receptor 3 (FGFR3) gene by restriction enzyme digestion analysis and direct sequencing using cultured amniotic fluid cells or cord blood cells revealed a missense mutation of 742C-->T (Arg248Cys) in all cases with TD1 and a missense mutation of 1948A-->G (Lys650Glu) in the case with TD2. The present report shows that adjunctive applications of molecular genetic analysis of the FGFR3 gene and three-dimensional ultrasound are useful for prenatal diagnosis of TD.     

Atelosteogenesis type II: sonographic and radiological correlation.

Atelosteogenesis type II is a lethal chondrodysplasia characterized by severe micromelia, spinal abnormalities, talipes equinovarus, and abducted thumbs and toes. We present a case diagnosed at 21 weeks of gestation in which antenatal sonographic and post-mortem radiological findings were correlated. The patient had a recurrence of this disorder in a subsequent pregnancy which was terminated at 15 weeks, supporting previous reports of an autosomal recessive inheritance pattern. The feasibility of diagnosing the following morphological features by prenatal ultrasonography is demonstrated: coronal clefts of the vertebral bodies, metaphyseal and epiphyseal abnormalities, spinal deviations such as cervical kyphosis and a horizontal sacrum, additional ossification centres in the pelvis, and preaxial deviation of the thumbs and toes. The differential diagnosis of this disorder from other skeletal dysplasias with similar features is discussed.     

Prenatal diagnosis of Apert syndrome

OBJECTIVE: The role of the human fibroblast growth factor receptor (FGFR) gene family in current prenatal diagnosis and management of craniosynostosis syndromes and skeletal dysplasias is discussed. METHOD: We present the antenatal ultrasound findings, diagnosis, and management of 2 cases of Apert syndrome before and after molecular prenatal diagnosis was available. RESULTS AND CONCLUSION: Discovery of mutations in FGFR genes now allows the definitive antenatal diagnosis of Apert syndrome, other craniosynostosis syndromes, and skeletal dysplasias.     

Sonographic and molecular diagnosis of thanatophoric dysplasia type I at 18 weeks of gestation

Thanatophoric dysplasia is the most common type of lethal skeletal dysplasia. It can usually be diagnosed with ultrasound, but differential diagnosis with other osteochondrodysplasias is not always possible. Mutations in the fibroblast growth factor receptor 3 (FGFR3) gene have been demonstrated to cause two distinct subtypes of the disorder. We describe a case of thanatophoric dysplasia type I diagnosed at 18 weeks of gestation by ultrasonography. Genomic DNA obtained by chorionic villus sampling showed a C to G substitution at position 746 in the FGFR3 gene, resulting in a Ser249Cys substitution already known to be associated with type I disease. Implications for perinatal management are discussed.     

Ultrasound findings of a rare congenital skeletal dysplasia: Stüve-Wiedemann syndrome

Stüve-Wiedemann syndrome (SWS) is an extremely rare congenital skeletal disorder associated with significant newborn mortality and morbidity in survivors. Prenatal diagnosis is reportedly possible, but a precise diagnosis is difficult because SWS is part of a heterogeneous group of bone dysplasias. Molecular analysis remains the gold standard for establishing a specific diagnosis of this kind of disorders and for providing effective prenatal counselling. This article presents a case of SWS suspected at prenatal ultrasound in the second trimester of pregnancy and confirmed by multidisciplinary approach at birth.     

Diagnóstico prenatal en el segundo trimestre de displasia torácica asfixiante

A case of prenatal diagnosis of Jeune’s syndrome is described. Because the incidence of this syndrome is low, diagnosis in the 21st week of pregnancy is exceptional. Jeune’s syndrome, or asphyxiating thoracic dysplasia, is a skeletal dysplasia with autosomal recessive inheritance. Prenatal diagnosis can be established by ultrasonographic findings of a small thorax, short ribs, pelvic abnormalities, rhizomelic brachymelia, and renal and liver anomalies, among others. In the present case, the prenatal diagnosis was confirmed at necropsy.     

Prenatal diagnosis of thanatophoric dysplasia by mutational analysis of the fibroblast growth factor receptor 3 gene and a proposed correction of previously published PCR results

Thanatophoric dysplasia (TD) is the most frequent form of neonatal lethal skeletal dysplasia. Recently. mutations in the fibroblast growth factor receptor 3 (FGFR3) gene that cause two subtypes of this disorder, type I (TDI) and type II (TDII), have been identified. This discovery has now made it possible to make a definite diagnosis of TD by molecular methods. To date, prenatal diagnosis of TD has been accomplished by ultrasonography in the second trimester. However, it is not always possible to distinguish TD fetuses it utero from the other osteochondrodysplasias by ultrasonography or radiography. We report on the prenatal diagnosis of a TD fetus, showing severe shortness of limbs and polyhydramnios, by identification of a mutation in the FGFR3 gene. Genomic DNA was isolated from the amniotic fluid and then subjected to PCR amplification. The common TDI mutation, C-->T transition at nucleotide 742 in the FGFR3 gene, was identified using restriction enzyme analysis. This information was critical in obstetric management decisions later in pregnancy. However, although the mutation responsible for TDI was detected previously, we noticed some inconsistencies in the published PCR results and have proposed a correction.     

A novel de novo mutation in COL2A1 gene associated with fetal skeletal dysplasia

ObjectiveSkeletal dysplasias, caused by genetic mutations, are a heterogenous group of heritable disorders affecting bone development during fetal life. Stickler syndrome, one of the skeletal dysplasias, is an autosomal dominant connective tissue disorder caused by abnormal collagen synthesis owing to a genetic mutation in COL2A1.Case reportWe present the case of a 38-year-old multipara woman whose first trimester screening showed a normal karyotype. However, the bilateral femur and humerus length symmetrically shortened after 20 weeks. Next-generation sequencing for mutations in potential genes leading to skeletal dysplasia detected a novel de novo mutation (c.1438G > A, p.Gly480Arg) in COL2A1, causing Stickler syndrome type 1. This pathogenic mutation might impair or destabilize the collagen structure, leading to collagen type II, IX, and XI dysfunction.ConclusionWe identified a novel de novo mutation in COL2A1 related to the STL1 syndrome and delineated the extent of the skeletal dysplasia disease spectrum.     

Congenital bowing of long bones: prenatal ultrasound findings and diagnostic dilemmas

OBJECTIVE: Bowing of the long bones can be easily detected on antenatal ultrasound screening, but it is a nonspecific sign that can be associated with a variety of conditions, each denoting a different prognosis. Among these conditions, three well-differentiated bone dysplasias share bowed long bones as a main clinical manifestation. Campomelic dysplasia and Stüve-Wiedemann syndrome are characterized by a poor prognosis. Conversely, the overall prognosis of children affected with kyphomelic dysplasia is good, the intelligence and motor development are normal and the radiological abnormalities tend to improve and regress with age. CASE REPORT: We report a case of prenatal detection of short and bowed femora at the 22nd week of gestation. Careful US examination as well as in utero X-ray of the skeleton allowed the exclusion of campomelic dysplasia. In the absence of an unambiguous diagnosis, the pregnancy was continued. At birth, the child presented with clinical and radiological features consistent with a diagnosis of kyphomelic dysplasia. CONCLUSION: This case illustrates the difficulties in making an accurate diagnosis and consequently giving a prognosis when isolated femoral bowing is found on fetal ultrasound examination.     

In utero ultrasonographic features of campomelic dysplasia

A prenatal diagnosis of campomelic dysplasia in a primigravida is described. First level fetal ultrasonography demonstrated bowing and shortening of lower limbs. Second level examination allowed the correct diagnosis by demonstrating several skeletal anomalies pathognomonic of campomelic dysplasia.     

Genotyping of the C742T mutation of the FGFR3 gene causing type 1 thanatophoric dysplasia by high-resolution melting analysis

Type 1 thanatophoric dysplasia (TD) is typically a lethal dwarfism. It is not always possible to distinguish fetuses with TD from other skeletal dysplasia in utero by ultrasonography. A definite diagnosis should be established by molecular genetic analysis to find out the abnormal mutations in the fibroblast growth factor receptor 3 (FGFR 3) gene. Among the known mutations of this gene, the C742T (R248C) mutation is the most common one associated with type 1 TD. Exon 7 of the FGFR3 gene was analyzed in 10 prenatal samples with type 1 TD, as well as in 30 control individuals for the presence of the c.742 C?>?T variant using melting curve analysis with a high-resolution melting instrument. The high-resolution melting curve analysis successfully genotyped this mutation in all 10 samples with type 1 TD without the need of further assays. The technique had a sensitivity and specificity of 100%. This study suggest that high-resolution melting analysis is a simple, rapid, and sensitive one tube assay for genotyping the FGFR3 gene.     

A novel nonsense mutation of TGFBR1 in a fetus with untypical Loeys-Dietz syndrome 1

ObjectiveWe present a rare untypical Loeys-Dietz syndrome 1 case in prenatal setting and report a novel mutation in the TGFBR1 gene.Case reportA pregnant woman came for medical attention due to the fetal ultrasound anomaly. The fetus was found to have short long bones. Trio-based WES was applied to the family. A novel de novo nonsense mutation c.1237C > T was detected in the TGFBR1 gene. A diagnosis of Loeys-Dietz syndrome 1 (LDS1) was plausible, but the fetus did not demonstrate the characteristic phenotype of the syndrome.ConclusionIn prenatal setting, fetal phenotypes are difficult to be fully observed, putting stress on the utility of molecular techniques. LDS1 in fetuses could present untypical features such as skeletal dysplasia.     

Ratios between growth parameters for the prenatal ultrasonographic diagnosis of skeletal dysplasias

The clinical applicability and usefulness of nine ratios that express the relation between particular fetal growth parameters were tested in ten fetuses affected by skeletal dysplasia. The results were compared with the ratios calculated from five growth-retarded fetuses without structural anomalies. Femur/foot, femur/head circumference, head circumference/thoracic circumference and abdominal circumference/thoracic circumference ratios are useful additional parameters for the prenatal ultrasonographic diagnosis of skeletal dysplasias. They reduce the problem of an unknown gestational age and help to distinguish between fetal skeletal dysplasia and intra-uterine growth-retardation caused by other factors.     

Prenatal three-dimensional ultrasound diagnosis of a camptomelic dysplasia

We describe a case of camptomelic dysplasia identified prenatally with the assistance of three-dimensional ultrasonography. The typical skeletal dysplasia of camptomelic dysplasia – including anterior bowing of the tibia, with skin dimpling over a convex surface at the point of maximal deformity, and talipes equinovarus – was successfully identified using the techniques of surface-rendering, multiplanar displays and rotated volume data. Three-dimensional ultrasonography allows the diagnosis of camptomelic dysplasia , which has a poor prognosis as it is accompanied by respiratory insufficiency and spinal deformities, to be made without delay and provides information supplementary to that provided by two-dimensional ultrasound for early diagnosis of skeletal dysplasia.