Usefulness of Early Genetic Diagnosis for Twins With a Family History of Congenital Nephrotic Syndrome.

We reported a dichorionic diamniotic placental twin (DD twin) with a family history of a congenital nephrotic syndrome of the Finnish type (CNF), of which the parent had heterozygous for the NPHS1 gene mutation. The DD twin was born at 36 weeks gestation, and their fused placenta weighed 1,340 g. Although the first-born child had heavy proteinuria and hypoalbuminemia and needed daily albumin replacement to manage severe edema, the second had only mild proteinuria after birth. Genetic testing performed 28 days after birth detected homozygous for the NPHS1 gene mutation in only the first-born child but not in the second, which resulted in performing invasive left nephrectomy and peritoneal dialysis (PD) to manage edema in the first. For DD twins with a family history of CNF, prenatal diagnosis of CNF may be difficult. Therefore, close postnatal clinical observation and early genetic testing are essential for the diagnosis of CNF.