Table 2.

Histological features of pregnancy-specific TMAs and pregnancy-associated TMAs.

TMA syndromes in pregnancy	Target organ of TMA	Characteristics of TMA lesions
		Morphologic changes/location	Preponderant mechanisms of capillaries obstruction
PE	Kidney +++ (rare in others organs except in eclampsia patients (25%) or in necropsy: liver, heart, adrenal)	Endothelial vacuolization, hypertrophy of the cytoplasmic organelles. Thrombi rich in fibrin are infrequent (severe disease). No vasculitis/Primary glomerular lesions, rare in arterioles	Swelling of EC and accumulation of subendothelial electrodense deposits
HELLP	Liver +++ Kidney	Fibrin deposition with periportal hemorrhage and hepatocyte necrosis/Sinusoids and portal tract capillaries, hepatic arteries, ± portal vein branches	Vasospasm, intraluminal fibrin and swelling of EC
TTP	CNS +++ Described in kidneys, adrenals, heart, liver, spleen. Few in GIT. Classically not in the lungs	Thrombi mainly consisted of aggregated platelets, relative absence of fibrin. No vasculitis, no fibrinoid necrosis/Diffuse in brain; Glomeruli, arterioles, and interlobular terminal arteries in kidney	Platelets thrombi rich in vWF and factor VIII Swelling of EC
CM-HUS	Kidney +++ Frequent: Colon, pancreas, myocardium, CNS Possible: adrenals, skin and lungs	EC swelling, subendothelial deposition of fibrinoid, thrombi rich in platelets with presence of fibrin. No vasculitis/Glomerular capillaries, afferent arterioles ± intralobular arteries	Platelets thrombi Swelling of EC
CAPS	Kidney lung, CNS, heart, skin, liver, GIT	Microthrombi composed of fibrin, acute necrotizing vasculitis. In chronic cases, these lesions can be accompanied by/small arteries and arterioles	Fibrin thrombi Intimal proliferation, EC swelling + frequent fibrous intimal hyperplasia
SLE	Kidney (except in TTP-like syndrome)	Microthrombi composed of fibrin, lesions related with LN (class IV ++ > III – V). Frequent immune complex deposits, leucocyte infiltration/Glomeruli, small arterioles ± arteries	TTP like: platelets thrombi Other cases: fibrin thrombi
DIC	Most affected organs (descending order): kidney, liver, lung, heart, pancreas, adrenal gland, and GIT	Diffuse multiorgan bleeding, hemorrhagic necrosis, fibrin microthrombi in small vessels, and thrombi in medium and large vessels. No vasculitis	Fibrin thrombi

CNS, central nervous system; EC, endothelial cells; GIT, gastrointestinal tractus; LN, lupus nephritis; vWF, von Willebrand factor.