Prenatal diagnosis of Fraser syndrome caused by novel variants of FREM2

A Rare Case of Complete Cryptophthalmos and Suspected Fraser's Syndrome in a Female Neonate

Cryptophthalmos is a rare congenital eye anomaly characterized by the absence of the palpebral fissure. Cryptophthalmos is often associated with Fraser's syndrome. We present a case of 3 days old female Asian neonate with complete unilateral cryptophthalmos, with the absence of a right eyelid. On inspection, there is an absence of eyelid, eyebrow and eyelashes in the right eye, collectively known as adnexal structures. The left eye was apparently normal. As per the parent's decision, surgical intervention was not pursued due to the poor visual prognosis. We advised prenatal genetic screening and testing for future pregnancies. These findings suggest the importance of genetic counseling and testing in cases of cryptophthalmos to identify potential genetic mutations and facilitate appropriate management.

Prenatal hydrometrocolpos as an unsual finding in fraser syndrome. Case report

Objectives

Fraser syndrome is a rare congenital malformation characterized by cryptophthalmos, syndactyly and urogenital tract malformations. The association with hydrometrocolpos is infrequent, with only a few cases reported in the literature.

Case presentation

A 19-year-old primigravida presenting at 35 weeks of gestation, with prenatal finding of hydrometrocolpos associated with hypotelorism and microphthalmia. Pre-term cesarean delivery was performed due to breech labor and perinatal death. The autopsy confirmed hydrometrocolpos secondary to vaginal atresia and imperforate hymen, associated with cryptophthalmos, syndactyly, nasal and pinna malformations, confirming the diagnosis of Fraser syndrome.

Conclusions

Fraser syndrome is usually a postnatal diagnosis. The association with genital abnormalities explains the finding of hydrometrocolpos, which could be considered a diagnostic criterion for this syndrome.

Identification of a HOXD13 variant in a Mongolian family with incomplete penetrance syndactyly by exon sequencing

Background

Syndactyly (SD) refers to a deformity caused by the fusion and limb differentiation disorder of soft tissues and/or skeletons to varying extents between adjacent fingers (toes). The main features of this disease are phenotypic heterogeneity and genetic heterogeneity. In this study, we examined four generations of a Chinese Mongolian with different phenotypes of syndactylia and analysed and identified the pathogenic genetic variants of SD by exon sequencing.

Methods

The clinical phenotypes of patients were analysed, and the hands and feet were examined by X-ray. The pedigree was drawn, and the family data were analysed. Peripheral blood was collected from the family members, and genomic DNA was extracted. The candidate genes of SD were identified by exon sequencing, and the mutation sites of the captured candidate genes were amplified by PCR and verified by Sanger sequencing.

Results

The family has congenital syndactyly, which is an autosomal dominant disease. At present, this condition has been passed down for 4 generations and was identified in 9 patients, including 4 males and 5 females. Five patients, I₂, II₄, III₅, III_,7 and III₁₀, had unilateral syndactyly, and four patients, III₁₆, IV₃, IV₆ and IV₇, had bilateral finger syndactyly. All of their toes were unaffected. The proband and the other patients in this family had a c.917G > A (p.R306Q) mutation, which is located at position 917 of the second exon of the HOXD13 gene. This mutation results in a change in the amino acid at position 306, in which arginine is changed to glutamine. This mutation cosegregates in unaffected individuals and affected patients in this family. Moreover, 201 Mongolian genome databases and a thousand human genome databases were referenced to further confirm that the pathogenic genetic variant that causes syndactyly in this family is found in HOXD13.

Conclusion

This study found that the mutation site of the pathogenic gene in this family was HOXD13, c.917G > A (p.R306Q). The phenotype of the family member III₁₂ was normal, but this member was also a carrier of the pathogenic genetic variant. This indicates that the disease of this family has incomplete penetrance characteristics. Our results further enrich the expression profile of the HOXD13 gene.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01360-3.

A multidisciplinary approach for prenatal diagnosis of FRASER SYNDROME-report of a novel variant in FRAS1

OBJECTIVE

With this case report, we would like to highlight the importance of a multidisciplinary approach and atypical findings of congenital high airway obstruction sequence (CHAOS), anhydramnios, and renal dysgenesis in the prenatal diagnosis of Fraser syndrome (FS).

CASE REPORT

A 25-year-old primigravida at 19 weeks of routine anomaly scan revealed abnormal sonographic findings such as fetal bilateral dysplastic small kidneys and gross oligohydramnios. The further detailed evaluation revealed that both fetal lungs were hyperechogenic with prominent (dilated) trachea and bronchi suggestive of CHAOS. Based on these findings, a diagnosis of FS was suspected. The couple was counseled and the pregnancy was terminated. The postmortem evaluation and novel homozygous variant in the FRAS1 gene confirmed the diagnosis of FS.

CONCLUSION

The diagnosis and counseling of the patient were supported by a well-coordinated, multidisciplinary approach involving an obstetrician, a fetal medicine specialist, a medical geneticist, and a fetal pathologist.

Developmental basis of trachea-esophageal birth defects

Trachea-esophageal defects (TEDs), including esophageal atresia (EA), tracheoesophageal fistula (TEF), and laryngeal-tracheoesophageal clefts (LTEC), are a spectrum of life-threatening congenital anomalies in which the trachea and esophagus do not form properly. Up until recently, the developmental basis of these conditions and how the trachea and esophagus arise from a common fetal foregut was poorly understood. However, with significant advances in human genetics, organoids, and animal models, and integrating single cell genomics with high resolution imaging, we are revealing the molecular and cellular mechanisms that orchestrate tracheoesophageal morphogenesis and how disruption in these processes leads to birth defects. Here we review the current understanding of the genetic and developmental basis of TEDs. We suggest future opportunities for integrating developmental mechanisms elucidated from animals and organoids with human genetics and clinical data to gain insight into the genotype-phenotype basis of these heterogeneous birth defects. Finally, we envision how this will enhance diagnosis, improve treatment, and perhaps one day, lead to new tissue replacement therapy.