Image source: JASN 2007
The immunofluorescence findings are somewhat variable with fibrin deposition often being a prominent feature.
The renal biopsy findings of preeclampsia closest to look in the context of the pathologic patterns seen in thrombotic microangiopathies (TMA). The lesions of preeclampsia share some similarities with and also some differences from those of non-preeclamptic TMA, likely owing to their differing pathogenesis.
What is the LM finding?
The glomeruli are enlarged and solidified (“bloodless”), as a result of narrowed or occluded capillary lumens that are the result of swelling of the native endothelial cells and, to a lesser extent, mesangial cells. The endothelial changes are limited to the glomerular capillaries; arterioles are typically unaffected. Thrombosis by light microscopy is decidedly unusual. In marked contrast, in nonpreeclamptic TMA, thrombosis of vessels and/or glomeruli is a central finding. Cases of severe preeclampsia with accompanying vascular thrombosis often have clinical signs suggesting a superimposed nonpreeclamptic TMA. In severe cases of preeclampsia, in particular as the lesions evolve/resolve, mesangial interposition can be seen, a finding shared with other entities resulting from chronic endothelial insult, such as “chronic” TMA or transplant glomerulopathy. So essentially, it may appear on LM in some cases- as an MPGN pattern of injury ( without the IF being positive for complements or immunoglobuins). This form of injury is termed “Glomerular endotheliosis”
What is the EM finding?
Ultrastructural analysis will show endothelial cells with loss of fenestrations with cytoplasmic swelling, owing to fluid and lipid accumulation and capillary occlusion.
What is the IF finding?
How is it different from your “classic” non preeclamptic TMA that you might see with SLE or APLAS or in TTP?
The main finding in the “classic” TMA is thrombosis of vessels and glomeruli as the main finding with some endotheliosis. This is a rare finding in pre-eclampsia related TMA unless it is very severe.
Here is a link to a nice review: