Dysfunction of dermal initial lymphatics of the arm and upper body quadrant causes congenital arm lymphedema

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.

Extended phenotypes of PIEZO1-related lymphatic dysplasia caused by two novel compound heterozygous variants

Defects in the PIEZO1 gene cause lymphatic dysplasia in an autosomal recessive manner, mostly by loss-of-function variants. Moreover, since 2019, the role of PIEZO1 in bone formation has been established, but there have been no PIEZO1-related cases presenting definite skeletal involvement to date. A 21-year-old male with primary lymphatic dysplasia had some other distinctive clinical features, including multiple fracture history during infancy, thoracolumbar scoliosis, short stature, and left-sided facial bone hypoplasia. We analyzed the whole exome of the patient and found two novel pathogenic variants of PIEZO1 in trans: a 93.7 kb heterozygous deletion (chr16:88,782,477-88,876,207; exon 1-50) and c.2858G>A (p.Arg953His). Sanger sequencing validated the deletion with breakpoints, and each variant was inherited from a different parent. This study presented an extremely rare case of a patient with lymphatic dysplasia caused by compound heterozygous variants of PIEZO1, along with additional clinical manifestations including several skeletal phenotypes.