Skeletal anomalies

Sonographic Detection of Skeletal Dysplasia

A case of skeletal dysplasia was sonographically evaluated in the fetus of a 21-year-old patient. The diagnosis of osteogenesis imperfecta type II was suggested during a routine morphological examination at 17 weeks’ gestation, based on visualization of rhizomelia, bowed long bones, and decreased thoracic cavity size. Sonographically, this dysplasia was well visualized and contributed to a final diagnosis, highlighting the diagnostic value of prenatal sonography. The use of routine sonographic examinations continues to prove crucial for early detection of fetal abnormalities such as skeletal dysplasias.

Sonographic markers for early diagnosis of fetal malformations

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a “genetic sonogram”, including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down’s syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).

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.

Pattern and prenatal diagnosis of skeletal dysplasias in Qatar population

OBJECTIVE

To determine the pattern of skeletal dysplasias in Qatar population and to assess the accuracy of prenatal diagnosis and prognosis.

METHODS

This was a retrospective descriptive study of 30 women with high risk for skeletal dysplasias. The recruited women were submitted to clinical assessment, ultrasound scanning using 2-dimensional, 3-dimensional/4-dimensional and colour Doppler technique with possible molecular diagnosis. The findings were compared with the postnatal or postmortem assessments. Final diagnosis was based on clinical examination, skeletal survey, autopsy and molecular testing as deemed necessary.

RESULTS

Thirty cases of skeletal dysplasia were antenatally diagnosed over 4-year period with family history in few cases. Among many entities thanatophoric dysplasia showed largest prevalence [7(23%)]. Prenatal diagnosis was accurate in 76% of foetuses while the first indicator of abnormality was a suspected anomaly found during routine ultrasound assessment in most cases [17(56%)]. Prediction of lethality based on ultrasound findings was 100% accurate.

CONCLUSIONS

This study confirmed the possibility of good prenatal diagnosis of skeletal dysplasias present among Qatar population. Diagnosis based on ultrasound assessment will improve by adding molecular techniques with positive impact on prenatal care.

My approach to performing a perinatal or neonatal autopsy

An opportunity to determine the cause of death, factors that may have a role in it, and the extent and cause of malformations is provided by perinatal autopsy. The family may be assisted in finding closure after the death of their infant by the information obtained. Insight into classifying infants appearing normal into one of three groups, small, appropriate and large for gestational age, has been provided, as each group tends to have specific causes of death. In infants with congenital anomalies, patterns of malformation may lead us to the diagnosis. An accurate diagnosis is required to provide counselling for a subsequent pregnancy.

Prenatal diagnosis of musculoskeletal anomalies

Musculoskeletal anomalies are not uncommon in prenatal life. They can be either sporadic or part of chromosomal syndromes causing prenatal morbidity and mortality. The prenatal diagnosis of musculoskeletal anomalies is based on information assembled from various imaging modalities and from biochemical and genetic workups. The prenatal diagnosis can serve as a prognostic tool and in counseling the parents. Among the imaging methods, ultrasonography is the most popular and cost effective in observing and following fetal development from the very early stages of gestation. Transvaginal sonography can detect and identify most of the normal and the specific pathologic changes very close to the stage of their embryogenic development. From a practical point of view, early detailed transvaginal sonography screening at 14 to 15 weeks of gestation is very useful while late detection at 20 to 23 weeks of gestation may provide some additional information in low-risk pregnancies. Very early screening, even during the ninth week, may be indicated in high-risk pregnancies. Additional genetic counseling is recommended when abnormal findings are suspected. We summarize the diagnostic approach and the information available for the most common musculoskeletal anomalies.

Prenatal diagnosis of fetal skeletal dysplasias by combining two-dimensional and three-dimensional ultrasound and intrauterine three-dimensional helical computer tomography

OBJECTIVE

To evaluate the contribution of new imaging techniques in the prenatal diagnosis of skeletal dysplasia.

METHODS

Between May and October 2003, a prospective study was conducted in a single referral center. Three-dimensional ultrasound (3D-US) and three-dimensional helical computer tomography (3D-HCT) were performed after two-dimensional ultrasound (2D-US) in six cases of skeletal dysplasia. Diagnostic accuracy and detailed findings with each of the three techniques were compared with postnatal radiological findings.

RESULTS

There were three cases of achondroplasia, two cases of osteogenesis imperfecta type II and one case of chondrodysplasia punctata. Termination of pregnancy was performed in five cases and one fetus with osteogenesis imperfecta type II was delivered at term by Cesarean section. 2D-US made the correct diagnosis in four cases. 3D-US and 3D-HCT achieved an accurate diagnosis in all six cases. 3D-HCT and 3D-US identified significantly more abnormalities than did 2D-US (3D-HCT: 94.3% (33/35); 3D-US: 77.1% (27/35); 2D-US: 51.4% (18/35); P < 0.01). The diagnosis was made between 27 and 36 weeks' gestation in all cases. The advantage of 3D-HCT over 3D-US was the possibility of imaging the entire fetus.

CONCLUSION

3D-US and 3D-HCT seem to be useful complementary methods to 2D-US, and may improve accuracy of the prenatal diagnosis of skeletal disorders. These new imaging technologies may have a role in the prenatal multidisciplinary approach to the diagnosis of skeletal dysplasias.

Variation of nanomechanical properties of bone by gene mutation in the zebrafish

Significant variations of nanomechanical properties and fracture morphology between gene-mutated liliput(dtc232) (lil/lil) zebrafish skeletal bone and wild-type bone have been observed. Nanoindentation measurement disclosed that lil/lil bone has 36% lower nanohardness and 32% lower elastic modulus. The standard deviations of hardness and elastic modulus of lil/lil bone were both much higher than those of wild-type bone. SEM morphology of fracture surfaces further revealed that in bones after gene mutation, formative microcracks make the performance reduction and the increasing of brittleness. What is more, the plywood-like structure of the normal bone does not exist in the lil/lil bone.