Bilateral Renal Hypoplasia with High β2-Microglobulinuria in the Neonatal Period

Urinary β2 microglobulin (β2-MG) is a low-molecular-weight protein that is filtered by the glomerular basement membrane and absorbed by the proximal tubule epithelial cells. In perinatal management, urinary β2-MG levels are used to assess intrauterine inflammation in newborns, since urinary excretion increases during inflammation. Furthermore, β2-MG levels in fetal blood and urine are also used for predicting fetal renal function because β2-MG is not transferred to the placenta. Herein, we reported a patient with persistent high urinary β2-MG levels since neonatal period, who was later diagnosed with bilateral renal hypoplasia. If a newborn presents persistent hyper β2-microglobulinuria even without hematuria or proteinuria, congenital renal malformations should be considered.