Prenatal sonographic diagnosis of skeletal dysplasias—a report of the diagnostic and prognostic accuracy in 35 cases

Genetic spectrum of prenatally diagnosed skeletal dysplasias in a Finnish patient cohort

OBJECTIVE

This retrospective cohort study aims to describe the genetic spectrum of fetal skeletal dysplasias detected in a Finnish patient cohort and the diagnostic yield of various analysis methods used.

METHOD

A total of 121 pregnancies with prenatally suspected or diagnosed skeletal dysplasia were analyzed between 2013 and 2020. Clinical details and findings from genetic testing were collected.

RESULTS

Abnormal ultrasound triggered further testing in most cases. However, there were several cases with increased nuchal translucency and/or abnormal risk ratio in the first trimester combined screening as the initial finding. Further genetic testing was performed in 84/121 (69.4%) cases. A genetic diagnosis was confirmed in 36/84 (42.9%) cases. Half of the identified cases could be attributed to a founder mutation specific to the Finnish Disease Heritage, whereas the other half consisted of a variety of other genetic defects.

CONCLUSION

In our patient cohort, the overall genetic spectrum of prenatally diagnosed skeletal dysplasias was wide. However, the impact of Finnish founder mutations was considerable, suggesting that the genetic spectrum of skeletal dysplasias may differ significantly between populations. This should be taken into consideration during the diagnostic process especially as initial ultrasound findings may be unspecific and the interpretation of ultrasound features is usually difficult.

The Application of Crown-Chin Length to Crown-Rump Length Ratio in Predicting Fetal Skeletal Dysplasia at First Trimester

OBJECTIVE

To examine the feasibility of using crown-chin length (CCL) to crown-rump length (CRL) ratio in screening for skeletal dysplasia in the first trimester.

METHODS

Four hundred and eighteen singleton pregnant women were recruited and the ratio of CCL to CRL was calculated according to gestational age. Fetuses with skeletal dysplasia were collected from database in the last 10 years. The CCL/CRL ratios were then calculated and the unpaired Student's t-test was to determine the significance of differences between normal fetuses and fetuses with skeletal dysplasia. Receiver operating characteristic curve was used to show the clinical sensitivity and specificity.

RESULTS

In 418 normal fetuses, CCL increased linearly with gestation from a mean of 20 mm at 11⁺⁰ weeks to 37 mm at 13⁺⁶ weeks (CCL [mm] = 0.51-4 CRL, R²  = 0.824, P = .000). There was also a significant linear association between fetal CCL/CRL ratio and CRL, from a mean of 0.48 at 11⁺⁰ weeks to 0.41 at 13⁺⁶ weeks (CCL/CRL = 0.63-3 CRL, R²  = 0.108, P = .000). In 154 skeletal dysplasia cases, early pregnancy ultrasound images were available in only 16 cases. The CCL/CRL ratio in 10 of 16 fetuses with skeletal dysplasia was above the 95th percentile. Using the 95th percentile as a cut-off, the detection rate, specificity, false-positive rate, and positive likelihood ratio are 62.5, 72.6, 5, and 17.5%, respectively.

CONCLUSIONS

Increased fetal CCL/CRL ratio at 11-14 weeks' gestation is associated with an increased risk of skeletal dysplasia and may be useful in first-trimester screening for this condition.

Fetal Skeletal Dysplasias: Radiologic-Pathologic Classification of 72 Cases

ObjectiveThe aim of this study was to classify the fetal skeletal dysplasias (FSD) in a series of affected fetuses based on radio-pathologic criteria. Materials and methods: We gathered clinicopathologic data of 72 cases which were diagnosed among 5995 autopsies performed over a 8-year period. Results: The prevalence of FSD was 1.2:100 autopsies. The overall sex ratio (M:F) was 1.25. Gestational age was between 17 and 24 weeks in 60% of cases. The FSD were classified into 13 distinct pathologic groups. Four major groups were identified: (1) Osteogenesis imperfecta (21 cases, 29%); (2) FGFR3 chondrodysplasia (18 cases, 25%); (3) Ciliopathies (9 cases, 12%); and (4) Sulfation disorders (7 cases, 10%). Thanatophoric dysplasia type 1 and lethal osteogenesis imperfecta were the most common skeletal dysplasias. Conclusion: Our study demonstrates the usefulness of the radio-pathologic examination in the diagnosis and accurate classification of the FSD, thus enabling better targeting of genetic counseling.

Early Gestational Diagnosis of Lethal Skeletal Dysplasias: A 15 Year Retrospective Cohort Reviewing Concordance between Ultrasonographic, Genetic and Morphological Features

Aim: We evaluated the diagnostic accuracy of ultrasound, postmortem and genetic studies in classifying skeletal dysplasias in the first vs second trimester of pregnancy. Methods: We retrospectively gathered data from a 15 year period of all the prenatal ultrasounds, autopsies, and available genetic studies on fetuses with skeletal dysplasias from our institution. Results: Five (23%) and 17 (77%) fetuses were diagnosed during the first and second trimester of pregnancy respectively. Only partial characterization was possible with ultrasound in the first trimester. Complete characterization was established in five cases (30%) in the second trimester with ultrasound alone. Pathology provided an additional diagnostic yield of 40% and 47% and genetics an additional 40% and 11% in the first and second trimesters respectively. Conclusion: Ultrasound is an effective screening but not a diagnostic tool. Complete characterizations of dysplasia increased from 22% by ultrasound alone to 86% with pathology and genetics.

Foetal thoracic hypoplasia: concomitant anomalies and neonatal outcomes

The aim of the current study was to determine the frequency of concomitant anomalies in foetal thoracic hypoplasia and the neonatal outcomes of these pregnancies. This retrospective study included 49 cases of foetal thoracic hypoplasia. All of the cases had skeletal system anomalies. Head and face anomalies (36.7%) were the second most frequent accompanying foetal anomaly, and the least common anomaly was genital system anomalies (4.1%). During the follow-ups, 52.6% (n = 10) of the newborns died in the first 24 h of life, 10.5% (n = 2) in the neonatal period and 36.8% (n = 7) in the infantile period.IMPACT STATEMENTWhat is already known on this subject? Foetal thoracic hypoplasias are lethal anomalies due to inadequate pulmonary development. Data on the other system anomalies that accompany foetuses with thoracic hypoplasia are quite limited in the literature. Moreover, even if the lethal course of thoracic hypoplasia is known, the information on how long newborns will survive is unclear.What do the results of this study add? In this study, most of the cases have additional anomalies, especially skeletal system and head-face anomalies. Approximately half of the newborns with thoracic hypoplasia die within the first 24 h.What are the implications of these findings for clinical practice and/or further research? When we need to consult a family considering the outcome of thoracic hypoplasia, this study can be guiding and helpful. On the other hand, the effects of additional anomalies on the prognosis of foetal and neonatal period are not clear. More studies are needed to better understand the prognosis of thoracic hypoplasias.

Anatomical Considerations of Embryology and Development of the Musculoskeletal System: Basic Notions for Musculoskeletal Radiologists

The musculoskeletal (MSK) system begins to form in the third week of intrauterine development. Multiple genes are involved in the complex different processes to form the skeleton, muscles and joints. The embryonic period, from the third to the eighth week of development, is critical for normal development and therefore the time when most structural defects are induced. Many of these defects have a genetic origin, but environmental factors may also play a very important role. This review summarizes the embryology of the different components of the MSK system and their configuration as an organ-system, analyzes the clinical implications resulting from failures in the process of organogenesis, and describes the first approach to diagnosis of skeletal abnormalities using prenatal ultrasound.

Imaging of Congenital Skeletal Disorders

Osteochondrodysplasias are the result of the expression of gene mutations. The phenotypes in osteochondrodysplasias evolve through life, with the possibility that previously unaffected bones may be involved at later stages of growth. Due to the variable time of onset, the diagnosis may be made prenatally, at birth, or later. Certainty in the diagnosis is sometimes only achieved as the patient matures and the disease evolves. Radiographic evaluation is a fundamental part of the diagnostic work-up of congenital skeletal disorders and in most cases the first tool used to arrive at a diagnosis. This review describes the imaging characteristics, specific signs, and evolution of several skeletal dysplasias in which diagnosis may be directly or indirectly suggested by radiologic findings. A definitive accurate diagnosis of a congenital skeletal abnormality is necessary to help provide a prognosis of expected outcomes and to counsel parents and patients.

Revisiting Skeletal Dysplasias in the Newborn

With over 400 reported disorders, the skeletal dysplasias represent a myriad of molecularly-based skeletal abnormalities. Arising from errors in skeletal development, the clinical spectrum of disease evolves through an affected individual's life. The naming and grouping of these disorders are ever-changing, but the fundamentals of diagnosis remain the same and are accomplished through a combination of prenatal ultrasonography and postnatal physical examination, radiography, and genetic analysis. Although some disorders are lethal in the perinatal and neonatal periods, other disorders allow survival into infancy, childhood, and even adulthood with relatively normal lives. The foundation of management for an affected individual is multidisciplinary care. Medical advances have offered new insights into reducing common morbidities through pharmacologic means. This review summarizes the normal skeletal development and discusses the 3 most common skeletal dysplasias that can affect the newborn.

Evaluation of exposure dose in fetal computed tomography using organ-effective modulation

Organ-effective modulation (OEM) is a computed tomography scanning technique that reduces the exposure dose to organs at risk. Ultrasonography is commonly used for prenatal imaging, but its reliability is reported to be limited. Radiography and computed tomography (CT) are reliable but pose risk of radiation exposure to the pregnant woman and her fetus. Although there are many reports on the exposure dose associated with fetal CT scans, no reports exist on OEM use in fetal CT scans. We measured the basic characteristics of organ-effective modulation (X-ray output modulation angle, maximum X-ray output modulation rate, total X-ray output modulation rate, and noise modulation) and used them in a Monte Carlo simulation to evaluate the effect of this technique on fetal CT scans in terms of image quality and exposure dose to the pregnant woman and fetus. Using ImPACT MC software, Monte Carlo simulations of OEMON and OEMOFF were run on 8 cases involving fetal CT scans. We confirmed that the organ-effective modulation X-ray output modulation angle was 160°; the X-ray output modulation rate increased with increasing tube current; and no modulation occurred at tube currents of 80 mA or below. Our findings suggest that OEM has only a minimal effect in reducing organ exposure in pregnant women; therefore, it should be used on the anterior side (OEMON,front) to reduce the exposure dose to the fetus.

Prenatal diagnosis of skeletal dysplasias using whole exome sequencing in China

BACKGROUND

Skeletal dysplasias account for nearly 10% of fetal structural malformations detected by ultrasonography. This clinically heterogeneous group of genetic anomaly includes at least 461 genetic skeletal disorders with extreme clinical, phenotypic, and genetic heterogeneities, thus, significantly complicates accurate diagnosis. Researches have used whole exome sequencing (WES) for prenatal molecular diagnoses of skeletal dysplasias, however, data are still limited.

METHODS

DNA extracted from umbilical cord blood or amniocytes from fetuses suspected of skeletal dysplasias based on ultrasound evaluations were analyzed by WES. Blood samples were taken from the parents of the positive fetuses for co-segregation analysis using Sanger sequencing.

RESULT

Definitive molecular diagnosis was made in 6/8 (75%) cases, comprised of 5 de novo disease-causing changes in 3 genes (FGFR3, COL2A1, and COL1A2) and one proband with a biallelic deficiency for Lamin B Receptor(LBR),and including 3 novel variants. All fetuses had no detectable copy number variation (CNV) from sequencing results.

CONCLUSIONS

Our study suggests that WES is an efficient approach for prenatal diagnosis of fetuses suspected of skeletal abnormalities and contributes to parental genetics counseling and pregnancy management.

Fetal magnetic resonance imaging of skeletal dysplasias

BACKGROUND

Fetal magnetic resonance imaging (MRI) is obtained for prenatal diagnosis and prognostication of skeletal dysplasias; however, related literature is limited.

OBJECTIVE

The purpose of this study was to define the utility of fetal MRI for skeletal dysplasias and to report MRI findings associated with specific diagnoses.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board; informed consent was waived. Women referred for suspected fetal skeletal dysplasia who underwent MRI between January 2003 and December 2018 were included. Definitive diagnoses were determined by genetic testing, autopsy, physical examination and/or postnatal/postmortem imaging. Fetal MRI examinations and reports were reviewed. Descriptive statistics were used to summarize imaging findings.

RESULTS

Eighty-nine women were referred for fetal MRI for possible skeletal dysplasia. Forty-three (48%) were determined to have a diagnosis other than skeletal dysplasia and nine were excluded for lack of specific skeletal dysplasia diagnosis. Thirty-seven cases of skeletal dysplasia with available fetal MRI and specific diagnosis were included for analysis. Diagnoses included achondrogenesis (n=2), achondroplasia (n=5), Boomerang dysplasia (n=1), campomelic dysplasia (n=2), Jeune syndrome (n=1), Kniest dysplasia (n=1), osteogenesis imperfecta (n=15) and thanatophoric dysplasia (n=10). A specific skeletal dysplasia diagnosis was mentioned in 17/37 (46%) of MRI imaging reports and correct for 14/17 (82%). MRI findings were reported for each specific skeletal dysplasia diagnosis.

CONCLUSION

Fetal MRI is a useful diagnostic tool for skeletal dyplasias and excluded the diagnosis in nearly half of referred pregnancies. In addition to providing fetal lung volumes, fetal MRI demonstrates findings of the brain in achondroplasia and thanatophoric dysplasia, of the spine in achondroplasia and achondrogenesis, of the calvarium in osteogenesis imperfecta and thanatophoric dysplasia, and of the cartilage in Kniest dysplasia.

Does prenatal counseling for pregnancies complicated by multiple fetal abnormalities concord with postnatal outcomes?

OBJECTIVE

In pregnancies complicated by multiple fetal abnormalities, our objective was to determine the degree of concordance between prenatal prognosis and postnatal outcomes.

METHOD

Retrospective cohort study of pregnancies with multiple fetal abnormalities referred to the Fetal Concerns Center of Wisconsin (FCCW) from 2015 to 2018. We reviewed records for anomalies, given prognostic severity, and postnatal outcomes. Prognostic severity was categorized as "likely mortality," "severe impairment," "moderate," and "mild" based on predetermined criteria.

RESULTS

In 85 pregnancies with multiple fetal abnormalities, 48% were given a prognosis of "likely mortality," and 19% were given a prognosis of "severe impairment." In pregnancies that were continued after being counseled as "likely mortality," this outcome was concordant in all but one case, despite medical interventions. In pregnancies counseled as "severe impairment," the more common outcome was mortality or severe impairment in 88% of cases and survival with severe impairment in 33% of cases. Postnatal outcomes were concordant with prenatal severity in 68% of the cases, more severe in 20% of the cases, and less severe in fewer than 5% of cases.

CONCLUSION

Prenatal predictions about severe outcomes are usually true in pregnancies complicated by multiple abnormalities. In cases of outcome discordance, outcomes tend to be more severe than predicted.

Best practice guidelines regarding prenatal evaluation and delivery of patients with skeletal dysplasia

BACKGROUND

Skeletal dysplasia comprises a heterogeneous and collectively common group of inherited disorders of development, growth, and maintenance of the human skeleton. There is potential for increased perinatal morbidity and mortality in pregnant women who themselves have skeletal dysplasia, and for affected fetuses where skeletal dysplasia is suspected in utero.

OBJECTIVE

We sought to establish guidelines for perinatal health care professionals who should be aware of these risks, to optimize maternal and child health pregnancy outcomes through best prenatal and delivery management practices.

STUDY DESIGN

A panel of 13 multidisciplinary international experts participated in a Delphi process, which comprised consideration of thorough literature review and a list of 54 possible care recommendations subject to 2 rounds of anonymous voting and a face-to-face meeting. Those recommendations with >80% agreement were considered as consensual.

RESULTS

During the first round, consensus was reached to support 30 out of the 54 statements. After the panel discussion, the group reached consensus on 40 statements. These statements include guidelines for the evaluation and treatment of pregnant women with skeletal dysplasia and for the unborn child with or suspected to have skeletal dysplasia.

CONCLUSION

Consensus-based best practice guidelines are provided as a minimum of standard care to minimize associated health risks, and improve clinical outcomes for patients with skeletal dysplasia.

Evaluating skeletal dysplasias on prenatal ultrasound: an emphasis on predicting lethality

Lethal skeletal dysplasias can be diagnosed by prenatal ultrasound (US) using several sonographic parameters. Degree of femoral shortening, lung volumes, femur length to abdominal circumference ratio, and chest circumference to abdominal circumference ratio are the most sensitive and specific predictors. Although there are more than 450 different skeletal dysplasias, only a few are lethal in the perinatal period. We review current fetal US literature and present an updated algorithmic approach to first establish lethality and, second, evaluate for hallmark sonographic features to help determine a specific diagnosis.

Foetal radiography for suspected skeletal dysplasia: technique, normal appearances, diagnostic approach

Despite advances in antenatal imaging and genetic techniques, post-delivery post-mortem foetal radiography remains the key investigation in accurate diagnosis of skeletal dysplasia manifesting in the foetus. Foetal radiography is best performed using pathology-specimen radiography equipment and is often carried out in the pathology department without involvement of the radiology unit. However, paediatric radiologists may be asked to interpret post-mortem foetal radiographs when an abnormality is suspected. Many foetal radiographs are carried out before 20 weeks' gestation, and the interpreting radiologist needs to be familiar with the range of normal post-mortem foetal appearances at different gestational ages, as well as the appearances of some of the more commonly presenting skeletal dysplasias, and will benefit from a systematic approach when assessing more challenging cases. In this pictorial essay, we illustrate various normal post-mortem foetal radiographic appearances, give examples of commonly occurring skeletal dysplasias, and describe an approach to establishing more difficult diagnoses.

Prenatal Sonographic Detection of Skeletal Dysplasias

Skeletal dysplasias are a genetically heterogeneous group of disorders that can be diagnosed prenatally by sonography. Differentiating these disorders in the prenatal period can be difficult. However, differentiating known lethal disorders from nonlethal disorders can improve patient care and plan of action. This case study presents multiple pterygia, flexion contractures, and skeletal abnormalities, which are consistent with multiple pterygium syndrome, or Escobar syndrome.

Widening of the femoral proximal diaphysis--metaphysis angle in fetuses with achondroplasia

OBJECTIVES

It has recently been reported that fetuses with achondroplasia have a wider than expected femoral proximal diaphysis-metaphysis angle (femoral angle). The aim of this case-control study was to investigate this finding.

METHODS

Cases with confirmed achondroplasia (n = 6), small-for-gestational-age fetuses (n = 70) and a group of normal fetuses (n = 377) were included in this study. The ultrasound image of the femur was examined by two independent experienced observers blinded to the diagnosis, who measured the femoral angle. These values were converted into multiples of the expected median (MoM), after adjustment for gestational age and femur length. Prevalence of various prenatal ultrasound signs of achondroplasia was determined in affected fetuses. Intra- and interobserver agreement of measurement of femoral angle was assessed using 95% limits of agreement and kappa statistics.

RESULTS

The femoral angle can be measured accurately by ultrasound, and increases with both increasing gestational age and increasing femur length. The femoral angle-MoM was significantly higher in fetuses with achondroplasia than in the control group (1.36 vs 1.00 MoM, P < 0.001) and in the SGA group (1.36 vs 1.04 MoM, P < 0.001). It measured more than 130° in five of the six cases with achondroplasia (83.3%), which was the most consistent finding other than shortening of the long bones.

CONCLUSIONS

The femoral angle is wider in fetuses with achondroplasia. This new ultrasound sign appears promising as an additional discriminatory marker when clinicians are faced with a case of short long bones in the third trimester.

Fetal skeletal dysplasias: sonographic indices associated with adverse outcomes

OBJECTIVES

To assess the utility of biometric indices and amniotic fluid volume in identifying fetuses with lethal skeletal dysplasia.

METHODS

A review of pregnancies with sonographic diagnosis of skeletal dysplasia between January 1997 and March 2012 from a single institution was conducted. Biometric indices and amniotic fluid volumes were reviewed from the initial targeted sonograms and all subsequent examinations. Outcomes were verified in all cases. Pregnancies that resulted in fetal or neonatal death were considered to have lethal dysplasia, and those with survival to hospital discharge were considered to have nonlethal dysplasia.

RESULTS

Of 45 fetuses with suspected skeletal dysplasia, 27 (60%) survived to hospital discharge; 9 (20%) died in the immediate neonatal period; 2 (4%) resulted in stillbirth; and in 7 cases (16%), pregnancy termination was elected. Those with lethal dysplasia were more likely to have hydramnios on initial detection than those who survived to hospital discharge (83% versus 27%; P < .01). Pregnancies complicated by lethal skeletal dysplasia had a significantly lower femur length-to-abdominal circumference ratio and were more likely to have a ratio below 0.16 than those with neonatal survival (91% versus 11%; P < 0.01). The lowest femur length-to-abdominal circumference ratio and the proportion with a ratio below 0.16 at any point in gestation were significantly different between those with lethal and nonlethal dysplasia (P< .01). As fetal size increased with advancing gestation, the relationship of sonographic parameters (eg, femur length-to-abdominal circumference ratio) became more pronounced. There was no infant survival when hydramnios was encountered at any point during gestation in the setting of a femur length-to-abdominal circumference ratio below 0.16.

CONCLUSIONS

In our series, a femur length-to-abdominal circumference ratio below 0.16 in conjunction with hydramnios effectively identified fetuses with lethal skeletal dysplasia.

Three-dimensional helical computed tomography in prenatal diagnosis of fetal skeletal dysplasia

OBJECTIVES

(1) To study the use and diagnostic value, as a complement to ultrasound, of helical computed tomography (helical CT) to differentiate normal fetuses from cases of skeletal dysplasia; (2) to define the most relevant indications for helical CT; and (3) to evaluate its diagnostic performance with respect to radiological criteria considered discriminatory.

METHODS

This was a retrospective study from 2005 to 2008 in 67 pregnant women who underwent helical CT after 26 weeks of gestation for suspected fetal skeletal dysplasia due to fetal shortened long bones on ultrasound (≤ 10(th) percentile), either alone or associated with other bone abnormalities. The results were compared with pediatric examinations in 41 cases and with fetal autopsy findings after elective termination of pregnancy in the others.

RESULTS

Helical CT had a sensitivity of 82%, specificity of 91% and positive and negative predictive values of 90% and 83%, respectively, for diagnosis of fetal skeletal dysplasia. An etiological diagnosis that had not been suspected at ultrasound was specified in 15% of cases and diagnoses suspected at ultrasound were confirmed in 24% and discounted in 43% of cases. The prevalence of skeletal dysplasia was increased in cases of micromelia < 3(rd) percentile or if there was a combination of bone signs. Helical CT showed 69% sensitivity in identifying individual predefined pathological bone signs which were confirmed on fetal autopsy findings.

CONCLUSION

Helical CT is a key examination, in combination with ultrasound, in the diagnosis of fetal skeletal dysplasia from 26 weeks of gestation. It should be reserved for cases with severe micromelia below the 3(rd) percentile and for those with micromelia ≤ 10(th) percentile associated with another bone sign. A checklist of discriminatory signs is proposed.

Safe, accurate, prenatal diagnosis of thanatophoric dysplasia using ultrasound and free fetal DNA

Objective

To improve the prenatal diagnosis of thanatophoric dysplasia by defining the change in fetal size across gestation and the frequency of sonographic features, and developing non-invasive molecular genetic diagnosis based on cell-free fetal DNA (cffDNA) in maternal plasma.

Methods

Fetuses with a confirmed diagnosis of thanatophoric dysplasia were ascertained, records reviewed, sonographic features and measurements determined. Charts of fetal size were then constructed using the LMS (lambda-mu-sigma) method and compared with charts used in normal pregnancies and those complicated by achondroplasia. Cases in this cohort referred to our Regional Genetics Laboratory for molecular diagnosis using cffDNA were identified and results reviewed.

Results

Forty-two cases were scanned in our units. Commonly reported sonographic features were very short and sometimes bowed femora, frontal bossing, cloverleaf skull, short fingers, a small chest and polyhydramnios. Limb shortening was obvious from as early as 13 weeks' gestation, with minimal growth after 20 weeks. Analysis of cffDNA in three of these pregnancies confirmed the presence of the c.742C>CT (p.Arg248Cys) or the c.1948A>AG (p.Lys650Glu) mutation in the fibroblast growth factor receptor 3 gene.

Conclusion

These data should improve the accuracy of the sonographic diagnosis of thanatophoric dysplasia and have implications for reliable and safe targeted molecular confirmation using cffDNA. © 2013 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.

Diagnosis and counseling of thanatophoric dysplasia with four-dimensional ultrasound

Thanatophoric dysplasia is a severe skeletal disorder with estimated frequency of 0.2-0.5 per 10,000 births. Affected infants die shortly after birth. The diagnosis of thanatophoric dysplasia can be made by two-dimensional ultrasound but the perception of these images is very difficult for the patients. The use of four-dimensional real time ultrasound gives the physician the possibility to discuss and counsel the patients with images that are more understandable to the general public.

FGFR3 related skeletal dysplasias diagnosed prenatally by ultrasonography and molecular analysis: presentation of 17 cases

Fibroblast Growth Factor Receptor 3 (FGFR3) related skeletal dysplasias are caused by mutations in the FGFR3 gene that result in increased activation of the receptors causing alterations in the process of endochondral ossification in all long bones, and include achondroplasia, hypochondroplasia, thanatophoric dysplasia, and SADDAN. Reports of prenatal diagnosis of FGFR3 related skeletal dysplasias are not rare; however, the correlation between 2nd trimester ultrasonographic findings and underlying molecular defect in these cases is relatively poor. There is a need for specific ultrasound (U/S) predictors than can distinguish lethal from non-lethal cases and aid an earlier prenatal diagnosis. Here we present one familial and 16 sporadic cases with FGFR3 related skeletal dysplasia, and we evaluate biometric parameters and U/S findings consistent with the diagnosis of skeletal dysplasia. U/S scan performed even at the 18th week of gestation can indicate a decreased rate of development of the femora (femur length (FL) <5th centile), while the mean gestational age at diagnosis is still around the 26th week. The utility of other biometric parameters and ratios is discussed (foot length, BPD, HC, FL/foot, and FL/AC). Prenatal cytogenetic and molecular genetic analyses were performed. A final diagnosis was reached by molecular analysis. In two cases of discontinued pregnancy, fetal autopsy led to a phenotypic diagnosis and confirmed the prenatal prediction of lethality. We conclude that the combination of U/S and molecular genetic approach is helpful for establishing an accurate diagnosis of FGFR3-related skeletal dysplasias in utero and subsequently for appropriate genetic counselling and perinatal management.

Prenatal diagnosis of skeletal dysplasias: contribution of three-dimensional computed tomography

OBJECTIVE

To describe the contribution of 3-dimensional computed tomography (3D-CT) in the prenatal diagnosis of skeletal dysplasias (SD) in a cohort of patients with inconclusive diagnosis by ultrasound (US).

METHODS

Between May 2007 and February 2010, six pregnant women with suspected fetal SD on US examination but with no specific diagnosis were studied with 3D-CT. The images were evaluated by a multidisciplinary team who proposed a likely diagnosis. Further postnatal workup included clinical and radiological evaluation in all cases. Prenatal and postnatal diagnoses were compared.

RESULTS

The use of 3D-CT provided a precise diagnosis confirmed postnatally in 5/6 patients. These included osteogenesis imperfecta type II (n = 2), osteogenesis imperfecta type III (n = 1), chondrodysplasia punctata (n = 1) and thanatophoric dysplasia type I (n = 1). A precise diagnosis could not be made in 1 case - either pre- or postnatally.

CONCLUSION

Prenatal 3D-CT contributed to the diagnosis of the specific fetal SD in the majority of these cases. 3D-CT may have a complementary role to US where fetal SD is suspected, but no specific diagnosis can be made using US alone. Further studies on clinical performance and risk-benefit analysis are needed.

Prenatal diagnosis of achondroplasia: new specific signs

BACKGROUND

Achondroplasia is one of the most common forms of short limb dwarfism. It is usually suspected on third trimester routine ultrasound because of very shortened long bones. We have described two new prenatal sonographic signs of achondroplasia visible at the proximal femoral metaphysis.

METHODS

Over 5 years, five fetuses were diagnosed with achondroplasia at the Grenoble Prenatal Diagnosis Centre. Ultrasound and tomographic examinations were performed by specialists. To study the proximal metaphysis, the ultrasound transducer was positioned at a 45 degree angle to the diaphyseal axis. Postnatal diagnosis was confirmed.

RESULTS

On computed tomography and postnatal X-ray, proximal femoral metaphysis appeared rounded, with poor, uneven ossification. Connexion to diaphysis was abnormal, with relative overgrowth of the periosteum, creating a new diagnostic sign that we called the 'collar hoop' sign. On ultrasound, all fetuses had a very rounded metaphyseal-epiphyseal interface, with an angle connexion to diaphysis wider than expected. The 'collar hoop' sign was obvious on four of the fetuses. During the same period, proximal femoral metaphyses appeared normal in 653 healthy fetuses, suggesting high specificity of those two new signs.

CONCLUSION

Metaphysis examination is recommended if fetal femur length measures below the fifth percentile, as normal aspect may rule out achondroplasia.

Prenatal sonographic diagnosis of skeletal dysplasias

OBJECTIVE

To assess the types and numbers of cases, gestational age at specific prenatal diagnosis and diagnostic accuracy of the diagnosis of skeletal dysplasias in a prenatal population from a single tertiary center.

METHODS

This was a retrospective database review of type, prenatal and definitive postnatal diagnoses and gestational age at specific prenatal diagnosis of all cases of skeletal dysplasias from a mixed referral and screening population between 1985 and 2007. Prenatal diagnoses were grouped into 'correct ultrasound diagnosis' (complete concordance with postnatal pediatric or pathological findings) or 'partially correct ultrasound diagnosis' (skeletal dysplasias found postnatally to be a different one from that diagnosed prenatally).

RESULTS

We included 178 fetuses in this study, of which 176 had a prenatal ultrasound diagnosis of 'skeletal dysplasia'. In 160 cases the prenatal diagnosis of a skeletal dysplasia was confirmed; two cases with skeletal dysplasias identified postnatally had not been diagnosed prenatally, giving 162 fetuses with skeletal dysplasias in total. There were 23 different classifiable types of skeletal dysplasia. The specific diagnoses based on prenatal ultrasound examination alone were correct in 110/162 (67.9%) cases and partially correct in 50/162 (30.9%) cases, (160/162 overall, 98.8%). In 16 cases, skeletal dysplasia was diagnosed prenatally, but was not confirmed postnatally (n = 12 false positives) or the case was lost to follow-up (n = 4). The following skeletal dysplasias were recorded: thanatophoric dysplasia (35 diagnosed correctly prenatally of 40 overall), osteogenesis imperfecta (lethal and non-lethal, 31/35), short-rib dysplasias (5/10), chondroectodermal dysplasia Ellis-van Creveld (4/9), achondroplasia (7/9), achondrogenesis (7/8), campomelic dysplasia (6/8), asphyxiating thoracic dysplasia Jeune (3/7), hypochondrogenesis (1/6), diastrophic dysplasia (2/5), chondrodysplasia punctata (2/2), hypophosphatasia (0/2) as well as a further 7/21 cases with rare or unclassifiable skeletal dysplasias.

CONCLUSION

Prenatal diagnosis of skeletal dysplasias can present a considerable diagnostic challenge. However, a meticulous sonographic examination yields high overall detection. In the two most common disorders, thanatophoric dysplasia and osteogenesis imperfecta (25% and 22% of all cases, respectively), typical sonomorphology accounts for the high rates of completely correct prenatal diagnosis (88% and 89%, respectively) at the first diagnostic examination.

A review of prenatally detected femoral abnormalities

Antenatally detected femoral abnormalities are a rare finding, and form a heterogeneous group in terms of diagnosis and prognosis. The objective of this study is to evaluate the management and outcome of fetuses after prenatal detection of femoral abnormalities in a tertiary care Fetal Medicine Unit over a 5-year period, thus facilitating accurate diagnosis and appropriate counseling. Patients were identified through a Regional Fetal Anomaly Database or clinician recall. Information was collected on whether the abnormality was an isolated or generalized skeletal abnormality, whether nonskeletal abnormalities were detected, what prognosis was counselled, whether referral to clinical genetics occurred, what investigations were performed, what was the eventual outcome and whether a final diagnosis was reached. A definitive diagnosis was made in 68% (28 of 41) of cases. However, a correct diagnosis was only achieved in 19% (eight of 41) of cases before delivery. Prognosis was correctly predicted in 83% (34 of 41) of cases. Families found the degree of uncertainty difficult, with 67% (six of nine) of patients where the prognosis was 'uncertain' electing to terminate the pregnancy. Eighty percent (eight of 10) of those where the condition was deemed 'lethal' also elected to end the pregnancy. In conclusion, it is difficult to achieve a correct diagnosis before delivery when a femoral abnormality is identified; however, detailed antenatal assessment may aid the differential diagnosis and help to determine prognosis. This was more likely to be achieved if the patient was seen in association with a clinical geneticist. A multidisciplinary team approach involving fetal medicine, genetics, paediatric radiology, and pathology is advocated. Fetal examination, medical photography, chromosomes and DNA storage, postnatal radiography and postmortem facilitate postnatal diagnosis and counseling.

Evaluation of prenatal-onset osteochondrodysplasias by ultrasonography: a retrospective and prospective analysis

The osteochondrodysplasias or skeletal dysplasias are a heterogenous group of over 350 distinct disorders of skeletogenesis. Many manifest in the prenatal period, making them amenable to ultrasound prenatal diagnosis. A retrospective analysis evaluated 1,500 cases referred to the International Skeletal Dysplasia Registry (ISDR) to determine the relative frequency of specific osteochondrodysplasias and correlation of ultrasound versus radiographic diagnoses for these disorders. Within the retrospective cohort of 1,500 cases, 85% of the referred cases represented well-defined skeletal dysplasias, and the other 15% of cases were a mixture of genetic syndromes and probable early-onset intrauterine growth restriction. The three most common prenatal-onset skeletal dysplasias were osteogenesis imperfecta type 2, thanatophoric dysplasia and achondrogenesis 2, accounting for almost 40% of the cases. In a prospective analysis of 500 cases using a standardized ultrasound approach to the evaluation of these disorders, the relative frequencies of osteogenesis imperfecta type 2, thanatophoric dysplasia and achondrogenesis 2 were similar to the retrospective analysis. This study details the relative frequencies of specific prenatal-onset osteochondrodysplasias, their heterogeneity of prenatal-onset skeletal disorders and provides a standardized prenatal ultrasound approach to these disorders which should aid in the prenatal diagnosis of fetuses suspected of manifesting skeletal dysplasias.

Short rib-polydactyly syndrome

INTRODUCTION

Short rib-polydactyly syndrome (SRPD) is an autosomal recessive, lethal skeletal dysplasia. It is characterized by short limb dwarfism, short ribs with thoracic hypoplasia, polydactyly, and multiple anomalies of major organs.

CASE REPORT

We report a case of SRPD subtype II (Majewski) that was detected in the 36th week of gestation, showing hydropic change, narrow thorax, shortened limbs, protuberant abdomen, micromelia, polydactyly and extremely low set ears, depressed nasal bridge, and cleft palate. The family was informed of the fatal outcome of the condition. Delivery was induced, and the baby died just after the birth.

DISCUSSION

Prenatal diagnosis is established with postmortem radiographic and pathologic examinations.

Evaluation of femur/foot and humerus/foot ratios by transvaginal sonography between 62 and 116 days of gestation

OBJECTIVE

The objective was to construct nomograms of femur/foot length and humerus/foot length ratios in early pregnancy by transvaginal sonography.

METHODS

In the period 1994-2000, 1,008 singleton pregnant patients were examined from 62 to 116 days of gestation using transvaginal high-resolution ultrasound technique. As a part of biometric survey femur, humerus and foot length were recorded and evaluated as ratio at each gestational age. The distribution of the residuals for the different ratios is also described.

RESULTS

A significant correlation was demonstrated between femur and foot length (R2=0.984; p<0.0001) and between humerus and foot length (R2=0.983; p<0.0001). The femur/foot length and humerus foot/length ratios were approximately 1 throughout this period of gestation with a narrow range.

CONCLUSION

The presented data obtained in early pregnancy by transvaginal scan offer normative measurements of femur/foot length and humerus foot/length ratios which may be useful in the prenatal diagnosis of congenital syndromes that include skeletal maldevelopment.

Prenatal diagnosis of isolated femoral bent bone skeletal dysplasia: problems in differential diagnosis and genetic counseling

Severe localized and symmetric bowing of the femora, in the absence of other significant skeletal or nonskeletal abnormalities, is a rare prenatal ultrasound finding. A 38-year-old woman was referred at 19 weeks gestation and ultrasound of the fetus showed severe shortening, and marked symmetric bowing of the femora. A provisional diagnosis of kyphomelic dysplasia (KD) was made. The patient elected termination of pregnancy and post mortem assessments were most consistent with kyphomelic dysplasia. KD is bent-bone skeletal dysplasia that, in contrast to campomelic dysplasia, involves principally the femora with relative sparing of the remainder of the skeleton. KD can be difficult to distinguish, particularly from symmetric cases of femoral hypoplasia unusual facies syndrome (FH-UFS), and few prenatal diagnoses have been reported. Because KD is thought to an be autosomal recessive disorder, the possibility that definitive diagnosis may not be possible prenatally, and even by postmortem assessment in cases choosing to abort, is an important counseling consideration.

Prenatal diagnosis of atelosteogenesis type I at 21 weeks' gestation

We describe prenatal diagnosis in a male fetus at 21 weeks of gestation with atelosteogenesis type I (AO I). Fetal ultrasonography (US) revealed absent or deficient ossification of the posterior neural arches of the thoracic spine, humeri, radii, ulnae, fibulae, and short tubular bones other than the distal phalanges, in addition to extremely short, thick femora. Fetal magnetic resonance imaging (MRI) using an ultrafast imaging sequence depicted dysmorphic features, pulmonary hypoplasia, and large cisterna magna. Postmortem radiographs warranted a diagnosis of AO I. Autopsy corroborated not only pulmonary hypoplasia but also laryngeal stenosis. The chondro-osseous histological findings were consistent with those of AO I. Meticulous evaluation using fetal US and MRI permits a definitive prenatal diagnosis of AO I to be made.

Prenatal sonographic diagnosis of skeletal dysplasias. A report of 47 cases

The purpose of this study was to evaluate the foetal sonographic efficiency for prenatal diagnosis of osteochondrodysplasias. Forty-seven prenatal and postnatal cases diagnosed between January 1993 and December 1998 in the referral sonographic centres of Strasbourg were studied. All cases were reviewed retrospectively and the prenatal ultrasound findings and diagnosis were compared to the postnatal or post-mortem diagnosis. Each case was studied by ultrasonographers, geneticists, radiologists, and foetopathologists. Final diagnosis was based on clinical examination, skeletal survey and molecular testing as deemed necessary. Routine screening and dating was the indication for foetal sonography in 72% (32/47) of our cases. The most likely time of diagnosis was between 16 and 24 weeks of gestation (17 out of 47 cases, 36%), which corresponds to the time of foetal anomaly sonographic scan in France. The other cluster of cases (12 among 47, 26%) was disclosed before 16 weeks of gestation. These results illustrate the importance of a detailed evaluation of the limbs during sonographic examinations of first and second trimesters of pregnancy. While the identification of skeletal dysplasias was relatively easy in our study, the ability to make an accurate specific antenatal diagnosis was more difficult. An accurate diagnosis was proposed in 28 of the 47 cases (60%). In 19% of the cases (9/47), the prenatal diagnosis was not accurate; in 21% of the cases (10/47), the prenatal diagnosis was imprecise. In 45 of the 47 cases (96%) prenatal foetal scan correctly predicted the prognosis.