Pathology of thrombotic thrombocytopenic purpura in the placenta, with emphasis on the snowman sign

Unfolding the pathophysiology of congenital thrombotic thrombocytopenic purpura in pregnancy: lessons from a cluster of familial cases

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP), a rare, potentially life-threatening thrombotic microangiopathy, manifests either as congenital TTP or acquired forms. It is caused by the absence or severe depletion of a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) protease, leading to the accumulation of ultra large von Willebrand factor multimers as well as extensive platelet adhesion and clumping, which can ultimately cause severe secondary end-organ damage. Pregnancy can provoke or exacerbate TTP, leading to maternal and fetal complications.

OBJECTIVE

In this report, we focused on pregnancy outcomes in a recently recognized cohort of congenital TTP patients of Bedouin Arab descent in southern Israel who were all homozygous for a novel c.3772delA variant of the ADAMTS13 gene, leading to the clinical manifestations of TTP largely during pregnancy.

STUDY DESIGN

All patients presented in this study belong to 2 closely related families of Arab Bedouin descent and were found to be homozygous for a novel ADAMTS13-c.3772delA variant. The cohort consisted of 19 females; 16 of them had congenital TTP and had been pregnant and were thus included. Patient data were collected from electronic medical records.

RESULTS

Of note, 13 women from our cohort, who delivered 14 fetuses (owing to 1 twin pregnancy), were diagnosed with congenital TTP following complicated pregnancies, which included recurrent pregnancy loss, stillbirth, early onset preeclampsia (both mild and severe), hemolysis, elevated liver enzymes and low platelet count syndrome, intrauterine growth restriction with abnormal Doppler flow, preterm premature rupture of membranes, and a total perinatal mortality rate of 30.7% (4/13). An additional 3 women, who were diagnosed owing to complications outside of pregnancy and at older ages, experienced TTP during their pregnancies, which occurred before diagnosis. Subsequent pregnancies were treated with fresh frozen plasma leading to a 100% fetal survival rate in the pregnancies that reached fetal viability. All placentas had lesions consistent with maternal vascular underperfusion. However, the severity and frequency of these lesions were lower in the 8 placentas from pregnancies treated with fresh frozen plasma.

CONCLUSION

This case series details a distinctive cohort of congenital TTP patients, all homozygous for the same, novel ADAMTS13 variant, who presented with clinical complications during pregnancy and maternal vascular lesions of underperfusion in the placenta. Our findings imply that the variant identified in the ADAMTS13 gene in our cohort may have a specific functional impact on the placenta, and that treatment with fresh frozen plasma during pregnancy ameliorates the course of the disease, leading to a milder phenotype or a normal pregnancy in the majority of cases.

Thrombotic thrombocytopenic purpura and acquired immunodeficiency syndrome diagnosed in pregnancy: Case report

Thrombotic thrombocytopenic purpura (TTP) is a medical emergency that demands prompt diagnosis to allow lifesaving treatment: plasmapheresis. TTP during pregnancy is rare, with estimated prevalence of 1/200 000, and even rarer in association with acquired immunodeficiency syndrome, with only two cases reported. Differential diagnosis includes HELLP syndrome (hemolysis elevated liver enzymes and low platelets), sepsis, intravascular-disseminated coagulation, and acquired autoimmune diseases, each one with its unique treatment and prognosis. A case of a pregnant woman at 26th week with sudden onset of left hand paresthesia and purpura is reported. PLASMIC score showed high risk for ADAMTS-13 deficiency and diagnosis of TTP was made. Human immunodeficiency virus screening test was positive on admission. Plasmapheresis and antiretroviral therapy were initiated and the delivery of a healthy newborn at full-term gestation was achieved, unlike other cases in literature. No obstetric complications were observed and the follow-up shows no signs of disease recurrence.

Placenta Accreta and Placenta Increta: An Approach to Pathogenesis Based on the Trophoblastic Differentiation Pathway

Morbid adherence remains a puzzling disease. This paper suggests that normal and morbidly adherent placentation may be viewed best in terms of trophoblastic stem cells and the mutually exclusive branches of the trophoblastic differentiation pathway-villous trophoblast (VT), interstitial and endovascular nonvillous trophoblast (NVT) at the implantation site, and a positional variation in the chorion. Based on cases of hysterectomies for morbid adherence seen over 30 years at a community hospital, analyzed with routine keratin stains, with actin and trichrome stains as indicated, and with attempts at ultrasonography-pathology correlation, we present selected observations. In true accreta, the site of morbid adherence was to dilated basal plate vessels infiltrated by endovascular NVT, with scant interstitial NVT, and normal myometrium. It appeared that excess blood flow into the placenta was due to excessively deep keratin-positive endovascular NVT that spread-independently of interstitial NVT-in an angiocentric fashion in both accreta and increta. Retroplacental abnormalities were due to myometrial destruction by interstitial NVT in increta, sometimes requiring actin stains for detection; and to an admixture of markedly dilated endometrial glands and vessels in true accreta, best appreciated with keratin stains. Variations of depth and extent in increta may be due to variations in myometrial tone, and in the protease-antiprotease balance. Morbidly adherent fetal membranes are described, and the role of caesarean section scars in incretas is addressed.

Imitators of severe pre-eclampsia

There are many obstetric, medial, and surgical disorders that share many of the clinical and laboratory findings of patients with severe pre-eclampsia-eclampsia. Imitators of severe pre-eclampsia-eclampsia are life-threatening emergencies that can develop during pregnancy or in the postpartum period. These conditions are associated with high maternal and perinatal mortalities and morbidities, and survivors may face long-term sequelae. The pathophysiologic abnormalities in many of these disorders include vasospasm, platelet activation or destruction, microvascular thrombosis, endothelial cell dysfunction, and reduced tissue perfusion. Some of these disorders include acute fatty liver of pregnancy, thrombotic thrombocytopenic purpura, hemolytic uremic syndrome, acute exacerbation of systemic lupus erythematosus, and disseminated herpes simplex and sepsis syndromes. Differential diagnosis may be difficult due to the overlap of several clinical and laboratory findings of these syndrome. It is important that the clinician make the accurate diagnosis when possible because the management and complications from these syndromes may be different. Because of the rarity of these conditions during pregnancy and postpartum, the available literature includes only case reports and case series describing these syndromes. This review focuses on diagnosis, management, and counseling of women who develop these syndromes based on results of recent studies and my own clinical experience.

Thrombotic thrombocytopenic purpura related to severe ADAMTS13 deficiency in children

Thrombotic thrombocytopenic purpura (TTP) related to a severely deficient activity of the von Willebrand factor cleaving protease, ADAMTS (A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats) 13, is a life-threatening event, the onset of which may occur as early as childhood. TTP is either inherited (Upshaw-Schulman syndrome) via ADAMTS13 gene mutations (neonatal onset) or acquired via anti-ADAMTS13 autoantibodies (childhood onset). TTP is due to platelet- and von-Willebrand-factor-rich thrombi of the microvasculature, inducing mechanical hemolytic anemia, consumption thrombocytopenia, and multivisceral ischemia. Clinical course consists of relapsing acute events triggered mostly by infections, associated icterus and hyperbilirubinemia, severe hemolytic anemia with schistocytosis and a negative Coombs test, severe thrombocytopenia, and sometimes symptoms related to visceral ischemia (renal failure, central nervous system vascular events, other organ failure). The recently available ADAMTS13 laboratory investigation combining measurement of ADAMTS13 activity in plasma, search for an ADAMTS13 circulating inhibitor, and anti-ADAMTS13 IgG and ADAMTS13 gene sequencing is a crucial addition to TTP diagnosis. Plasma exchanges are first-line treatment of acquired TTP, combined with steroids and immunosuppressive drugs. Curative treatment of acute events in Upshaw-Schulman syndrome relies on plasma infusions (provider of active ADAMTS13). Guidelines for preventive treatment of relapses are not clearly established but should associate plasmatherapy and caution to triggers of relapses. Therapeutic perspectives are focused on the development of concentrated plasma-derived ADAMTS13 or recombinant ADAMTS13.