Morphological demonstration of non-heme iron and iron-binding proteins in placentas from cases of congenital nephrotic syndrome of Finnish type.

Two placentas (gestational age 36 and 39 weeks respectively), obtained from Congenital Nephrotic Syndrome of Finnish type (CNF) cases, have been studied by histochemistry in relation to the presence of non-heme iron and iron-binding proteins (ferritin, transferrin and lactoferrin). Ten control placentas of gestational age ranging from 35 to 40 weeks have been also examined. Employing the Prussian Blue ferrocyanide method, an intense positive reaction of the trophoblastic basament membrane (TBM) was observed only in cases of CNF. By immunoperoxidase techniques, ferritin was demonstrated in the villous stroma whereas lactoferrin was identified only in the cytoplasm of polymorphonuclear neutrophils within fetal stem vessels; a clear positivity for transferrin was encountered on the apical site of the syncytial trophoblast. All these immunohistochemical findings were similar in CNF cases and in control placentas. Ultrastructural observations of terminal villi revealed the presence of osmiophilic granulo-filamentous hemosiderin-like bodies in TBM of placentas from CNF. Although the role of iron-binding proteins in the iron transport through the placenta seems to be unaltered in CNF, the presence of non-heme iron in TBM could represent a histochemical approach for placental diagnosis in this type of nephrotic syndrome.