Prenatal ultrasound diagnosis of rhizomelic chondrodysplasia punctata in a primigravida

Prenatal Sonographic Three-dimensional Virtual Organ Computer-assisted Analysis Thymic Volume Calculation May Predict Intrauterine Growth Restriction

Background

Intrauterine growth restriction (IUGR) refers to fetuses that are small for their gestational age. There is no effective test to predict this disease. The aim of our study is whether fetal three-dimensional (3D) ultrasonography (USG)-assisted thymus volume (TV) measurement predicts IUGR cases.

Methods

Fetal 3D USG thymus measurement between 15 and 24 weeks of gestation was performed in a total of 100 women of reproductive age. Fetal TV was measured using the virtual organ computer-assisted analysis system program. All cases were followed up in terms of pregnancy complications until delivery.

Results

IUGR was developed in six cases in total. In cases with IUGR, mean fetal TV was found to be statistically significantly lower than in healthy cases without it. When the fetal TV was taken as 0.1645, the sensitivity was calculated as 89.5% and the specificity as 50% for predicting IUGR. The use of low fetal volume parameters is a significant and good indicator for predicting IUGR according to the binary logistic regression analysis result.

Conclusion

According to the results of this study, 3D fetal TV measurement may be used in routine second-trimester sonographic anomaly screening to predict the development of fetal IUGR. In this way, fetal mortality and morbidity caused by IUGR may be reduced.

A new GNPAT variant of foetal rhizomelic chondrodysplasia punctata

Background

Rhizomelic chondrodysplasia punctata (RCDP) is a clinical entity resulting from defects of peroxisomal metabolism whose clinical phenotype is characterized by rhizomelia, calcified foci in periarticular cartilage, coronal lesions of vertebral bodies, cataracts and severe cognitive delay. Usually, survival does not exceed the first decade of life. Transmission is autosomal recessive and is related to mutations in the PEX7, GNPAT or AGPS.

Methods

A detailed description of the prenatal ultrasound signs of RCDP found in two successive pregnancies in a consanguineous couple is reported. Molecular genetic investigations included the study of the coding regions and the exon–intron junctions of the GNPAT (high‐throughput amplification and sequencing performed with Roche NimbleGen SeqCap Target kit on Illumina platform); the confirmation test was carried out by amplification and Sanger sequencing with automatic capillary sequencer.

Results

In addition to the typical prenatal ultrasound signs described in the literature in association with RCDP, the presence of prefrontal oedema, never previously described, has been detected in both pregnancies. Moreover, genetic investigations have found a new splicing variant c.924+1G>A of the homozygous GNPAT.

Conclusion

The role of mutation in the GNPAT suggests a likely association with the clinical phenotype.

Peroxisomes in brain development and function

Peroxisomes contain numerous enzymatic activities that are important for mammalian physiology. Patients lacking either all peroxisomal functions or a single enzyme or transporter function typically develop severe neurological deficits, which originate from aberrant development of the brain, demyelination and loss of axonal integrity, neuroinflammation or other neurodegenerative processes. Whilst correlating peroxisomal properties with a compilation of pathologies observed in human patients and mouse models lacking all or individual peroxisomal functions, we discuss the importance of peroxisomal metabolites and tissue- and cell type-specific contributions to the observed brain pathologies. This enables us to deconstruct the local and systemic contribution of individual metabolic pathways to specific brain functions. We also review the recently discovered variability of pathological symptoms in cases with unexpectedly mild presentation of peroxisome biogenesis disorders. Finally, we explore the emerging evidence linking peroxisomes to more common neurological disorders such as Alzheimer’s disease, autism and amyotrophic lateral sclerosis. This article is part of a Special Issue entitled: Peroxisomes edited by Ralf Erdmann.

Fetal thymus volume estimation by virtual organ computer-aided analysis in normal pregnancies

OBJECTIVES

The thymus has a pyramidal shape, which is best shown in coronal planes. The aim of this study was to evaluate the potential of virtual organ computer-aided analysis to estimate fetal thymus volume in normal pregnancies.

METHODS

Three-dimensional volume data sets from the axial upper mediastinal section were acquired from 37 normal pregnancies between 12 and 35 weeks' gestation. Thymus volume was calculated by virtual organ computer-aided analysis by 2 separate examiners. In 12 cases, volumes were also acquired with 4-dimensional sonography and spatiotemporal image correlation software to assess the variability in thymus size between the systolic and diastolic periods of fetal heart motion. Linear regression analysis was used to assess the relationship between the fetal thymus volume and gestational age. Paired Student t tests were used to evaluate both the level of agreement for interobserver and intraobserver variability and the difference between diastolic and systolic thymus volumes.

RESULTS

Identification of the borders of the thymus and calculation of its volume were successful in 28 patients (77.7%). Statistically significant linear growth of the thymus during pregnancy, from 12 to 35 weeks, was found. The growth coefficient for each gestational age was 0.43 (95% confidence interval, 0.355 to 0.504; P < .001). The difference in thymus size between systole and diastole was minor (0.0798 cm(3); 95% confidence interval, -0.044 to 0.203 cm(3)). Interobserver and intraobserver variability was not statistically significant.

CONCLUSIONS

Although the thymus has a complex shape, it was possible to determine its borders and to calculate its volume by virtual organ computer-aided analysis in 77.7% of cases. Linear growth during pregnancy was found, and the minor changes during systole and diastole could be explained by condensation of the soft tissue of the thymus secondary to cardiac activity.

Prenatal diagnosis of brachytelephalangic chondrodysplasia punctata: case report

Brachytelephalangic chondrodysplasia punctata is a rare congenital skeletal dysplasia. Within the heterogeneous group of chondrodysplasia punctata, the brachytelephalangic type is noteworthy because it has a better prognosis than do the other types. We report a case of brachytelephalangic chondrodysplasia punctata diagnosed by ultrasound imaging at 30 weeks' gestation; it was associated with polyhydramnios and a normal cervical spinal canal. Imaging features are described and differential diagnosis with other forms of chondrodysplasia punctata is discussed.

Diameter of the normal fetal thymus on ultrasound

OBJECTIVE

To present the normative data of the transverse diameter of the developing fetal thymus.

METHODS

In this prospective study, the maximum transverse diameter of the thymus was measured by one sonologist in 376 normal fetuses between 19 and 38 weeks of gestation. We assessed the relationship of the transverse thymic diameter with gestational age (GA), biparietal diameter, femur length and abdominal circumference using general linear regression modeling. The predicted mean and 95% reference range of thymic diameter at each GA were calculated from the regression equation.

RESULTS

Measurements of the transverse diameter were possible in 352 of the 376 (94%) fetuses. The transverse diameter of the fetal thymus increased with increasing GA and fetal size parameters in a linear manner. The regression equation for transverse diameter of the thymus as a function of GA was: thymic diameter (cm) = 0.15 x GA (weeks) - 1.59 (r(2) = 0.86, P < 0.001).

CONCLUSION

The transverse diameter of the fetal thymus is easy to measure; this study presents normative data.

Peroxisome biogenesis disorders

Defects in PEX genes impair peroxisome assembly and multiple metabolic pathways confined to this organelle, thus providing the biochemical and molecular bases of the peroxisome biogenesis disorders (PBD). PBD are divided into two types--Zellweger syndrome spectrum (ZSS) and rhizomelic chondrodysplasia punctata (RCDP). Biochemical studies performed in blood and urine are used to screen for the PBD. DNA testing is possible for all of the disorders, but is more challenging for the ZSS since 12 PEX genes are known to be associated with this spectrum of PBD. In contrast, PBD-RCDP is associated with defects in the PEX7 gene alone. Studies of the cellular and molecular defects in PBD patients have contributed significantly to our understanding of the role of each PEX gene in peroxisome assembly.

Prenatal Ultrasonographic Diagnosis of Rhizomelic Chondrodysplasia punctata by Detection of Rhizomelic Shortening and Bilateral Cataracts

Antenatal sonographic diagnosis of rhizomelic chondrodysplasia punctata depends on recognization of the combination of rhizomelic bone shortening and epiphyseal stippling. This is the only report of prenatal ultrasonographic diagnosis of bilateral cataracts in a fetus with rhizomelic chondrodysplasia punctata (type 1). Also, this is the first report of severe rhizomelic limb shortening, and bilateral cataracts prior to the recognization of epiphyseal stippling.

Fetus with an unusual form of nonrhizomelic chondrodysplasia punctata: case report and review

Chondrodysplasia punctata (CDP) is a heterogeneous condition mainly characterized by premature and ectopic calcification of cartilage. Many genetic and nongenetic causes have been described leading to a preliminar etiological classification into defects of peroxisomal metabolism, defects in cholesterol metabolism, and vitamin K (vit K) metabolism. However, numerous cases of CDP still remain unclassified. The difficulties in reaching a causal diagnosis are illustrated here by a 23-week-old fetus with nonrhizomelic CDP characterized by extensive cartilage stippling, brachyphalangy, and nasal hypoplasia.

The development of the fetal thymus: an in utero sonographic evaluation

OBJECTIVES

To establish a nomogram for fetal thymus size during gestation.

METHODS

The study is a prospective, cross sectional evaluation of 403 male and female fetuses between 14 and 38 weeks of normal singleton pregnancies. Measurements of fetal thymus size were performed by high resolution transvaginal ultrasonography between 14 and 17 weeks' gestation, and by transabdominal ultrasonography after 18 weeks' gestation.

RESULTS

Adequate thymus size measurements were obtained in all 403 fetuses. Thymus size as a function of gestational age was expressed by the regression equation: (square root) thymus size (mm)= -39.39+4.41 x gestational age (weeks). The correlation coefficient, r=0.965, was found to be highly statistically significant (p<0.0001). The normal mean and the 90% prediction limits were defined.

CONCLUSION

The present data offer the normal range of fetal thymus size from early stages of gestation that may allow intrauterine assessment of its development. It may be helpful in the prenatal diagnosis of thymic pathologies.

Prenatal diagnosis of rhizomelic chondrodysplasia punctata due to isolated alkyldihydroacetonephosphate acyltransferase synthase deficiency

Current practices in prenatal diagnosis of rhizomelic chondrodysplasia punctata (RCDP) are reviewed. A case is presented with a family having one daughter affected with RCDP due to alkyldihydroacetonephosphate acyltransferase synthase (DHAPAT synthase) deficiency, and three subsequent pregnancies. Biochemical test values are presented for the pregnancies and daughter. Post-mortem tests of one fetus of a terminated pregnancy showed that radiologic examination could not make the diagnosis of RCDP. We conclude that biochemical or molecular testing is necessary to accurately diagnose this type of RCDP prenatally.