Recurrent prenatal PIEZO1-related lymphatic dysplasia: Expanding molecular and ultrasound findings

Investigation into the genetics of fetal congenital lymphatic anomalies

OBJECTIVE

Congenital lymphatic anomalies (LAs) arise due to defects in lymphatic development and often present in utero as pleural effusion, chylothorax, nuchal and soft tissue edema, ascites, or hydrops. Many LAs are caused by single nucleotide variants, which are not detected on routine prenatal testing.

METHODS

Demographic data were compared between two subcohorts, those with clinically significant fetal edema (CSFE) and isolated fetal edema. A targeted variant analysis of LA genes was performed using American College of Medical Genetics criteria on whole exome sequencing (WES) data generated for 71 fetal edema cases who remained undiagnosed after standard workup.

RESULTS

CSFE cases had poor outcomes, including preterm delivery, demise, and maternal preeclampsia. Pathogenic and likely pathogenic variants were identified in 7% (5/71) of cases, including variants in RASopathy genes, RASA1, SOS1, PTPN11, and a novel PIEZO1 variant. Variants of uncertain significance (VOUS) were identified in 45% (32/71) of cases. In CSFEs, VOUS were found in CELSR1, EPHB4, TIE1, PIEZO1, ITGA9, RASopathy genes, SOS1, SOS2, and RAF1.

CONCLUSIONS

WES identified pathogenic and likely pathogenic variants and VOUS in LA genes in 51% of fetal edema cases, supporting WES and expanded hydrops panels in cases of idiopathic fetal hydrops and fluid collections.

Perinatal presentations of non-immune hydrops fetalis due to recessive PIEZO1 disease: A challenging fetal diagnosis

Hydrops fetalis is a rare disorder associated with significant perinatal complications and a high perinatal mortality of at least 50%. Nonimmune hydrops fetalis (NIHF) is more frequent and results from a wide variety of etiologies. One cause of NIHF is lymphatic malformation 6 (LMPHM6) due to biallelic loss-of-function (LoF) variants in PIEZO1. Most individuals are diagnosed postnatally and only few clinical data are available on fetal presentations. We report six novel biallelic predicted LoF variants in PIEZO1 identified by exome sequencing in six fetuses and one deceased neonate from four unrelated families affected with LMPHM6. During the pregnancy, most cases are revealed by isolated NIHF at second trimester of gestation. At post-mortem examination ascites, pleural effusions and telengectasies can guide the etiological diagnosis. We aim to further describe the perinatal presentation of this condition which could be underdiagnosed.

Pediatric Lymphedema: Study of 180 Patients Referred to a Tertiary Lymphedema Clinic

BACKGROUND

Lymphedema is due to dysfunction of the lymphatic system. It can be primary or secondary. Pediatric lymphedema is more often primary and is a chronic disease with a heavy burden on quality of life.

METHODS

Medical records of patients under 18 years of age referred between 1996 and 2021 to the specialized lymphedema clinic at the Sainte-Justine University Hospital Center were reviewed. Demographic data, sex, age at presentation, location of the lymphedema, clinical features, genetic testing, symptoms, complications, investigations, and treatment were collected.

RESULTS

Of 180 referred patients, lymphedema was confirmed in 151, and 137 were primary lymphedema. Median age of apparition of primary lymphedema was 7.00 years and was significantly lower in boys than in girls. Primary congenital lymphedema was more frequent in boys (51.0%, 27.3% in girls, P = .007), and onset of primary lymphedema during adolescence was more frequent in girls (53.4%, 25.0% in boys, P = .001). Lower limbs were the most impacted (88.3%). Sixty patients had genetic testing, and 38 (63.3%) of them were discovered to have a pertinent genetic mutation. The most common mutated gene was the FLT4 gene (in 9 patients). Seven patients (5.1%) had associated extensive/central lymphatic malformation and 24 (17.6%) had a polymalformative syndrome/syndromic lymphedema.

CONCLUSIONS

Pediatric lymphedema is more frequent in girls, usually involves lower limb, and is most often sporadic, but often associated with a genetic mutation, and genetic testing should be performed.

A Novel Homozygous Missense Mutation of PIEZO1 Leading to Lymphatic Malformation-6 Identified in a Family With Three Adverse Pregnancy Outcomes due to Nonimmune Fetal Hydrops

Lymphatic malformation-6 (LMPHM6) is a rarer form of nonimmune hydrops that often manifests as widespread lymphedema involving all segments of the body, namely, subcutaneous edema, intestinal/pulmonary lymphangiectasia, chylothoraces, and pleural/pericardial effusions. Here, we detected one rare and previously unobserved homozygous missense variant in PIEZO1 (c.5162C>G, p.Ser1721Trp) as a novel genetic cause of autosomal recessive LMPHM6, in a family with three adverse pregnancy outcomes due to nonimmune fetal hydrops. Although, the loss-of-function mutations such as those usually including nonsense, frameshift, splice site, and also fewer missense variants in PIEZO1 have been proved to lead to LMPHM6, among these, the biallelic homozygous mutations resulting in the loss of function of PIEZO1 have not been reported before. Here, we first strongly implicated impaired PIEZO1 function–associated LMPHM6 with a homozygous missense mutation in PIEZO1.

PIEZO1 mutation: a rare aetiology for fetal ascites

We present a case of isolated fetal ascites diagnosed at 20 weeks' gestation. No aetiology was identified on extensive prenatal workup, including prenatal microarray. The patient terminated the pregnancy at 23 weeks' gestation. Exome sequencing was performed on the products of conception, which ended up giving insight into a possible cause for the ascites. Two heterozygous missense variants of uncertain significance were identified in the PIEZO1 gene. The paternal variant has been linked to dehydrated hereditary stomatocytosis. The father of the baby suffers from haemolytic anaemia, splenomegaly and has had jaundice throughout his life. His brother and father have similar conditions. We suspect that at least one of the gene variants identified in our exome sequencing may be responsible for the illness that runs in this family, including the fetus with isolated ascites.