Discovery of pathogenic variants in EFEMP2 and RAG1 and undetectable fetal phenotype: A challenge of prenatal exome sequencing.

BACKGROUND: Exome sequencing in prenatal context confronts with pathogenic variants associated with phenotypes that are not detectable prenatally. MATERIALS AND METHODS: A consanguineous couple was referred at 24 weeks of gestation for prenatal genetic investigations after ultrasonography findings including decreased fetal movements, hypoplastic male external genitalia, retrognathia, prefrontal edema, anomalies of the great vessels with pulmonary atresia and dilated tortuous aorta. RESULT: Prenatal trio exome sequencing identified two homozygous likely pathogenic variants, i.e. a missense in EFEMP2 involved in cutis laxa and a nonsense in RAG1 involved in several types of severe combined immunodeficiency. DISCUSSION: The fetal ultrasonographic phenotype was partially compatible with previously reported prenatal presentations secondary to EFEMP2 biallelic variants, but prenatal presentations have never been reported for RAG1 related disorders because the RAG1 phenotype is undetectable during pregnancy. CONCLUSION: Both EFEMP2 and RAG1 variants were disclosed to the couple because the EFEMP2 variant was considered causative for the fetal ultrasonographic phenotype and the RAG1 variant was considered a finding of strong interest for genetic counselling and monitoring of future pregnancies following the American College of Medical Genetics and Genomics recommendations about the discovery of incidental findings in fetal exome sequencing in prenatal diagnosis.

Acute fetal leukemia: When should it be suspected? What assessment should be performed? A case series and review of literature.

INTRODUCTION: Acute fetal leukemia is rare and characterized by a very poor prognosis. The aims of this study were to identify cases of acute fetal leukemia and to describe ultrasound and fetopathological findings that should lead to a suspicion of this diagnosis, as well as the investigations required to confirm it. METHODS: A national retrospective study was conducted. Clinical data, prenatal ultrasounds and postmortem findings of fetal acute leukemia cases were collected and analyzed. RESULTS: We collected seven cases: four in utero fetal deaths, two neonatal deaths and one termination of pregnancy. Prenatal ultrasounds showed fetal hydrops (42.9%) associated with hepatosplenomegaly (100%). In addition, post-mortem examination (n = 6) suggested a Down syndrome in one case and showed other organomegaly (83.3%) due to blastic infiltration, mainly in the liver, along with extrahepatic multivisceral hematopoiesis. Immunostainings allowed to specify the type of leukemia (71.4%). In one case, diagnosis was made on blood smear and flow cytometry was performed on fresh blood samples. All cases corresponded to acute myeloid leukemia. Karyotype was abnormal in 4 cases (66.7%), including one free trisomy 21, two mosaic trisomy 21 and one chromosome 15 deletion. GATA1 gene mutations were identified in two cases: one mosaic trisomy 21 and one with normal karyotype. CONCLUSION: Any hepatosplenomegaly associated with fetal hydrops and a negative immune, infectious, and metabolic work-up, should suggest acute fetal leukemia and prompt additional investigations.

Early prenatal diagnosis of causative homozygous variants in ASCC1 in a fetus with cystic hygroma and additional homozygous variants of unknown significance associated with a neurological phenotype not visible in early gestation: Dual diagnosis or not?

A consanguineous couple was referred at 10 weeks of gestation (WG) for prenatal genetic investigations due to isolated cystic hygroma. Prenatal trio exome sequencing identified causative homozygous truncating variants in ASCC1 previously implicated in spinal muscular atrophy with congenital bone fractures. Prenatal manifestations in ASCC1 can usually include hydramnios, fetal hypo-/akinesia, arthrogryposis, contractures and limb deformities, hydrops fetalis and cystic hygroma. An additional truncating variant was identified in CSPP1 associated with Joubert syndrome. Presentations in CSPP1 include cerebellar and brainstem malformations with vermis hypoplasia and molar tooth sign, difficult to visualize in early gestation. A second pregnancy was marked by the recurrence of isolated increased nuchal translucency at 10 + 2 WG. Sanger prenatal diagnosis targeted on ASCC1 and CSPP1 variants showed the presence of the homozygous familial ASCC1 variant. In this case, prenatal exome sequencing analysis is subject to a partial ASCC1 phenotype and an undetectable CSPP1 phenotype at 10 weeks of gestation. As CSPP1 contribution is unclear or speculative to a potentially later in pregnancy or postnatal phenotype, it is mentioned as a variant of uncertain significance. The detection of pathogenic or likely pathogenic variants involved in severe disorders but without phenotype-genotype correlation because the pregnancy is in the early stages or due to prenatally undetectable phenotypes, will encourage the clinical community to define future practices in molecular prenatal reporting.