Altered immunoglobulin status in congenital nephrotic syndrome

The serum and urine immunoglobulin concentrations of a patient with congenital nephrotic syndrome of the Finnish type (CNS) were studied during an 11 month period. The serum IgG levels were never higher than 25% and most were below 2% of normal infant values. Serum IgM levels rose to three times normal and IgA concentrations varied. The selective protein index (SPI) showed apparent selective proteinuria (SPI less than 0.06). Intravenous gamma-globulin infusions were carried out to raise serum IgG levels. The infused IgG was initially contained within the intravascular space, but within 30 hours 55% was lost in the urine. Compared to the steady state, the renal clearance of IgG showed a 20-fold increase immediately post-infusion. We conclude that children with CNS should be considered essentially agammaglobulinemic throughout the first year of life and perhaps longer. Intravenous IgG infusions provide only hours of sufficient IgG replacement due to rapid urinary losses and may be detrimental.