Nephrotic syndrome due to preeclampsia before 20 weeks of gestation: a case report

BACKGROUND: Preeclampsia (PE) refers to the development of hypertension and new-onset proteinuria or progressive organ damage (especially kidney) in a previously normotensive pregnant women after 20 weeks of gestation. Thus, new-onset nephrotic syndrome due to PE before 20 weeks of gestation seems to be rare, making its diagnosis difficult in this time period. CASE PRESENTATION: A 28-year-old woman presented with a new-onset nephrotic syndrome at 16 weeks of gestation. A high dose of oral glucocorticoids (prednisolone, 40 mg) was initiated for presumed glomerulonephritis since she presented with severe nephrotic syndrome before 20 weeks of gestation, however, the treatment was not effective. At 21 weeks of gestation, we confirmed that the soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratio was very high (sFlt-1, 13,400 pg/mL; PlGF, 21.9 pg/mL; serum sFlt-1/PlGF ratio 611.9). Therefore, we diagnosed nephrotic syndrome due to PE, and oral glucocorticoids were discontinued. After she underwent a cesarean section at 24 weeks & 3 days, we performed a kidney biopsy. Focal segmental sclerotic lesions with epithelial cell hyperplasia and foam cells in the tubular poles were seen on light microscopy. On immunofluorescence tests, C4d staining showed linear peripheral patterns in the glomeruli. Electron microscopy revealed diffuse subendothelial edema with focal foot process effacement. The histological diagnosis was severe glomerular endotheliosis with focal segmental glomerulosclerosis. Furthermore, the histology of placenta was consistent with PE. Eight months after delivery, her proteinuria disappeared completely. CONCLUSIONS: We not only confirmed an abnormal serum sFlt-1/PlGF ratio but also presented the histology compatible with pure PE in the kidney and placenta in a case of nephrotic syndrome before 20 weeks of gestation. The serum sFlt-1/PlGF ratio may be useful in determining the treatment strategy for atypical cases of pregnant women with nephrotic syndrome, particularly before 20 weeks of gestation.