Perinatal Stroke and Cerebral Sinovenous Thrombosis Caused by Congenital Nephrotic Syndrome NPSH1 (Finnish Type): A Case Report

Congenital nephrotic syndrome (CNS) is a severe renal disorder in newborns, characterized by complications such as albuminuria, hypoalbuminemia, and hypercoagulability. While CNS is known to predispose patients to thrombosis over time, to our knowledge, cerebrovascular complications such as cerebral sinovenous thrombosis (CSVT) within the first week after birth have rarely been reported before in neonates with confirmed CNS. We present here an infant, born by normal vaginal delivery, which was complicated by the retention of a large placenta. She was first admitted on day 3 with perioral cyanosis and polycythemia. She developed apneas that were later confirmed with amplitude integrated EEG to be seizures and was found to have multiple thrombotic complications, including extensive CSVT and bilateral thalamic hemorrhages. Serum albumin level was very low, with high urinary levels suspicious for Finnish-type CNS, which was confirmed by <i>NPHS1</i> pathogenic variants p.Cys623Phe and p.Asn870Profs*36. Despite partial exchange transfusions and anticoagulation therapy, the infant developed severe cerebral abnormalities. This case underscores the importance of considering CNS in neonates with a large placenta, severe polycythemia, proteinuria, and hypoalbuminemia, as they may be at risk of developing CSVT.