In a recent article in AJKD, Al-Rabadi et al present a case of a pregnancy patient with active membranous nephropathy (MN) and circulating autoantibodies to PLA2R, the major autoantigen in primary MN. Despite the presence of low titer circulating IgG1, IgG3, and IgG4 anti-PLA2R antibodies at the time of delivery, the fetus showed no proteinuria. This contrasts with previous observations that trans-placental passage of circulating autoantibodies can result in neonates showing clinical manifestations of systemic lupus erythematosus, myasthenia gravis, and membranous nephropathy secondary to anti-neutral endopeptidase antibodies.
This phenomenon could not be explained by mopping up of antibody by the placenta since attempts to elute out antibody from this tissue were unsuccessful. The possibility that other organs in the fetus acted as a sponge for antibody is not excluded. Moreover, since no kidney biopsy was performed subclinical membranous nephropathy remains a possibility. The authors are justifiably cautious about concluding that pregnancy is universally safe in nephrotic patients with active PLA2R-associated MN. It is possible that the fetus might be affected in mothers with higher antibody titers than those observed in this patient.
Paramjeet Randhawa, MD
AJKD Blog Contributor