Prenatal diagnosis of Desbuquois dysplasia Type 1: Utilization of high-density SNP array to map homozygosity and identify the gene

Prenatal diagnosis and postnatal outcome of fetal congenital knee dislocation: systematic review of literature

OBJECTIVES

Congenital knee dislocation (CKD) is a rare condition, affecting 1 in 100 000 newborns. Its prenatal diagnosis is challenging and not well described in the literature, especially when it appears isolated and not as part of a complex malformation or syndromic pattern. The purpose of this study was to provide a comprehensive review of the available literature on the prenatal diagnosis and postnatal outcome of CKD and to summarize the current evidence on this topic.

METHODS

A systematic review of the literature on the prenatal diagnosis of CKD was performed in PubMed, Scopus and EMBASE. A predefined combination of specific keywords was used, focusing on intrauterine manifestations, diagnostic methods, prenatal behavior, postnatal treatment and neonatal outcome as well as long-term outcome in terms of ambulation, motion and joint stability. The quality of studies was assessed using the National Institutes of Health tool for quality assessment of case series. A summary of results was carried out providing proportions and rates of diagnostic and prognostic features associated with this rare condition.

RESULTS

In total, 20 cases were retrieved for analysis, of which 19 were obtained from the identified eligible studies (n = 16) and one was an unpublished case from our center. The median gestational age at prenatal diagnosis, which was made using ultrasound in most cases, was 20 weeks (range, 14-38 weeks). Bilaterality was observed in 11/20 (55%) cases. The condition was isolated in 7/20 (35%) cases and associated with other anomalies in 13/20 (65%) cases. An association was observed with oligohydramnios (4/20 (20%)), and an invasive procedure was performed in 13/20 (65%) cases, including 11 cases with an invasive procedure performed for diagnostic purposes. Genetic testing was normal in all isolated cases for which information was available (4/7), while a genetic syndrome was present in 10/13 (77%) non-isolated cases (Larsen, Noonan, Grebe, Desbuquois or Escobar syndrome). There were seven terminations of pregnancy, of which six were performed in cases with associated anomalies and one in an isolated case, 11 cases of postnatal survival, one case of intrauterine death and one of neonatal death. The fetal and neonatal deaths occurred in cases with associated anomalies or abnormal genetic findings. Postnatal treatment was mostly conservative, with only two reports (18% of the 11 surviving neonates) of surgical intervention, both in cases with associated anomalies. Postnatal follow-up was up to 1 year in most cases, and motor outlook appeared normal in all isolated cases.

CONCLUSIONS

CKD is a rare fetal anomaly with a prenatal diagnosis achievable from the early second trimester, for which a favorable outcome can be expected when no associated anomalies are present. Prenatal diagnosis should include detailed ultrasound assessment and amniocentesis for extensive genetic studies, particularly in non-isolated cases. Early postnatal treatment achieves success in most cases without surgical intervention and leads to a normal motor outlook. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Antenatal Phenotype of Desbuquois Dysplasia

Desbuquois dysplasia (DBQD) is an uncommon, autosomal recessive disorder with multiple joint dislocations. It is caused by pathogenic variants in CANT1 (calcium-activated nucleotidase 1) [NM_001159773.2]. This study adds to the scant data of nine reported antenatal phenotypes of DBQD. The present paper describes two unrelated consanguineous families with antenatal features of lethal skeletal dysplasia. The defining radiological changes were identified in only one patient who presented in the late second and third trimesters. Solo exome sequencing was performed and two previously reported homozygous variants c.896C>T (p.Pro299Leu) in patient 1 and c.902_906dup (p.Ser303fs*20) in patient 2 were identified. This study highlights the fetal presentations in DBQD and adds to its phenotypic spectrum. A complete clinical workup, including fetal autopsy and radiographs is essential to confirm the diagnosis of lethal skeletal dysplasia. Molecular diagnosis remains the diagnostic modality to define the causative variant. A definitive diagnosis is essential to inform management and offer reproductive care.

First Report of Two Egyptian Patients with Desbuquois Dysplasia due to Homozygous CANT1 Mutations

Desbuquois dysplasia type 1 (DBQD1) is a very rare skeletal dysplasia characterized by growth retardation, short stature, distinct hand features, and a characteristic radiological monkey wrench appearance at the proximal femur. We report on 2unrelated Egyptian patients having the characteristic features of DBQD1 with different expressivity. Patient 1 presented at the age of 45 days with respiratory distress, short limbs, faltering growth, and distinctive facies while patient 2 presented at 5 years of age with short stature and hypospadias. The 2 patients shared radiological features suggestive of DBQD1. Whole-exome sequencing revealed a homozygous frameshift mutation in the CANT1 gene (NM_001159772.1:c.277_278delCT; p.Leu93ValfsTer89) in patient 1 and a homozygous missense mutation (NM_138793.4:c.898C>T; p.Arg300Cys) in patient 2. Phenotypic variability and variable expressivity of DBQD was evident in our patients. Hypoplastic scrotum and hypospadias were additional unreported associated findings, thus expanding the phenotypic spectrum of the disorder. We reviewed the main features of skeletal dysplasias exhibiting similar radiological manifestations for differential diagnosis. We suggest that the variable severity in both patients could be due to the nature of the CANT1 gene mutations which necessitates the molecular study of more cases for phenotype-genotype correlations.

Radiographic findings of Desbuquois dysplasia

Desbuquois dysplasia is an autosomal recessive chondrodysplasia characterized by severe micromelic dwarfism, joint laxity, progressive scoliosis, and advanced carpotarsal ossification. Two different types of Desbuquois dysplasia have been identified according to the presence (Type 1) or absence (Type 2) of characteristic hand abnormalities including bifid distal thumb phalanx, an extra ossification center distal to the second metacarpal, and interphalangeal joint dislocations. Further, Kim et al have described a milder variant of Desbuquois dysplasia characterized by short stature and hands with short metacarpals, elongated proximal and distal phalanges, and extremely advanced carpal ossification. Here, we present a 19-year-old male patient with Kim variant of Desbuquois dysplasia. He displays almost all of the characteristic skeletal findings of Desbuquois dysplasia along with the characteristic hand features described by Kim et al. This patient is unique in that he also presents sagittal femoral bowing, a radiographic finding that accompanies various skeletal dysplasias but has never been reported in a patient with Desbuquois dysplasia to date.

Molecular testing strategies in the evaluation of fetal skeletal dysplasia

OBJECTIVE

The aim of this study was to characterize the fetal sonographic findings and the approach utilized to obtain a definitive diagnosis through molecular testing strategies.

METHODS

This is a retrospective case series of fetuses referred for consultation for prenatal findings suggestive of a skeletal dysplasia between March 1, 2014 and March 1, 2016. Ultrasound images, their timing in gestation and reported findings were reviewed and skeletal abnormalities were documented. Unique features were ascertained. The approach for molecular evaluation, and molecular results were extracted.

RESULTS

Nine cases were referred for evaluation secondary to prenatal sonographic features suggestive of a skeletal dysplasia. In 4 cases a skeletal dysplasia was suspected prior to 16 weeks gestation. Three of these, with mutations in CANT1, NEK1, and COL2A1 were considered lethal, while the fourth case had a non-lethal ALPL mutation. Similarly 2 of 3 cases diagnosed at 16-22 weeks gestation had lethal mutations in COL1A and DYNC2H1 while the fetus with Russell Silver survived. The final 2 cases diagnosed in the third trimester, both hypochondroplasia, were non-lethal dysplasias. A molecular diagnosis was obtained in 8/9 (88.9%) cases which encompassed eight different skeletal dysplasias. The final case declined molecular testing.

CONCLUSION

Features of specific skeletal dysplasias can be visualized in utero and guide appropriate molecular testing. Sonographic details in addition to molecular genetic results aid in prognostic counseling.