The impact of congenital thrombotic thrombocytopenic purpura on pregnancy complications

Clinical Manifestations, Current and Future Therapy, and Long-Term Outcomes in Congenital Thrombotic Thrombocytopenic Purpura

Congenital thrombotic thrombocytopenic purpura (cTTP) is an extremely rare disease characterized by the severe deficiency of a disintegrin and metalloproteinase with thrombospondin type 1 motifs 13 (ADAMTS13), caused by ADAMTS13 mutations. While ADAMTS13 supplementation by fresh frozen plasma (FFP) infusion immediately corrects platelet consumption and resolves thrombotic symptoms in acute episodes, FFP treatment can lead to intolerant allergic reactions and frequent hospital visits. Up to 70% of patients depend on regular FFP infusions to normalize their platelet counts and avoid systemic symptoms, including headache, fatigue, and weakness. The remaining patients do not receive regular FFP infusions, mainly because their platelet counts are maintained within the normal range or because they are symptom-free without FFP infusions. However, the target peak and trough levels of ADAMTS13 to prevent long-term comorbidity with prophylactic FFP and the necessity of treating FFP-independent patients in terms of long-term clinical outcomes are yet to be determined. Our recent study suggests that the current volumes of FFP infusions are insufficient to prevent frequent thrombotic events and long-term ischemic organ damage. This review focuses on the current management of cTTP and its associated issues, followed by the importance of upcoming recombinant ADAMTS13 therapy.

A Race against the Clock: A Case Report and Literature Review Concerning the Importance of ADAMTS13 Testing in Diagnosis and Management of Thrombotic Thrombocytopenic Purpura during Pregnancy

Thrombocytopenic purpura (TTP) is a rare, potentially fatal pathology characterized by microangiopathic thrombotic syndrome and caused by an acute protease deficiency of von Willebrand factor, ADAMTS13. Moreover, ADAMTS13 deficiency promotes microthrombosis led by the persistence of ultra-large VWF multimers in the blood circulation. According to the few studies involving pregnant participants, the heterogeneity of manifestations has made this pathology difficult to diagnose, with an unexpected occurrence and increased risk of maternal and fetal morbidity and mortality. We reported on the case of a 28-year-old pregnant woman with an obstetric score of G2P0 who presented to the obstetrics and gynecology department of our clinic with the complaint of minimal vaginal bleeding. The evolution of our case was severe and life-threatening, a “race against the clock”, with our goal being to emphasize the importance and difficulty of diagnosing TTP in the absence of specific symptomatology. We faced a lack of technological support for a correct and complete diagnosis, and the first manifestation of this disease was the intrauterine death of the fetus. After completing all the necessary procedures, the placental tissue was sent for further histopathological evaluation. We highlighted the importance of monitoring ADAMTS13 for relapses monthly, with prophylaxis being essential for maternal and fetal mortality and morbidity.

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.

Annual incidence and severity of acute episodes in hereditary thrombotic thrombocytopenic purpura

Hereditary thrombotic thrombocytopenic purpura (hTTP) is a rare thrombotic microangiopathy characterized by severe congenital ADAMTS13 deficiency and recurring acute episodes causing morbidity and premature death. Information on the annual incidence and severity of acute episodes in patients with hTTP is largely lacking. This study reports prospective data on 87 patients from the Hereditary TTP Registry (clinicaltrials.gov #NCT01257269) for survival, frequency, and severity of acute episodes from enrollment until December 2019. The 87 patients, followed up for a median of 4.2 years (range, 0.01-15 years), had a median age at overt disease onset and at clinical diagnosis of 4.6 years and 18 years (range, 0.0-70 years for both), respectively. Forty-three patients received regular plasma prophylaxis, whereas 22 did not, and treatment changed over time or was unknown in the remaining 22. Forty-three patients experienced 131 acute episodes, of which 91 (69%) occurred in patients receiving regular prophylaxis. This resulted in an annual incidence of acute episodes of 0.36 (95% confidence interval [CI], 0.29-0.44) with regular plasma treatment and of 0.41 (95% CI, 0.30-0.56) without regular plasma treatment. More than one-third of acute episodes (n = 51) were documented in children <10 years of age at enrollment and were often triggered by infections. Their annual incidence of acute episodes was significantly higher than in patients aged >40 years (1.18 [95% CI, 0.88-1.55] vs 0.14 [95% CI, 0.08-0.23]). The prophylactic plasma infusion regimens used were insufficient to prevent acute episodes in many patients. Such regimens are burdensome, and caregivers, patients, and their guardians are reluctant to start regular plasma infusions, from which children particularly would benefit.

Insights from the Hereditary Thrombotic Thrombocytopenic Purpura Registry: Discussion of Key Findings Based on Individual Cases from Switzerland

The Hereditary TTP Registry is an international cohort study for patients with a confirmed or suspected diagnosis of hereditary thrombotic thrombocytopenic purpura (hTTP) and their family members. Hereditary TTP is an ultra-rare blood disorder (prevalence of ∼1-2 cases per million), the result of autosomal-recessively inherited congenital ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) deficiency (ADAMTS13 activity <10% of the normal), and associated with yet many unanswered questions. Until December 2017, the Hereditary TTP Registry had enrolled 123 confirmed hTTP patients. Their median age at disease onset was 4.5 years (range: 0-70) and at clinical diagnosis 16.7 years (range: 0-69), a difference that highlights the existing awareness gap in recognizing hTTP. The systematic collection of clinical data of individual patients revealed their substantial baseline comorbidities, as a consequence of recurring TTP episodes in the past. Most notable was the high proportion of patients having suffered from premature arterial thrombotic events, mainly transient ischemic attacks, ischemic strokes, and to a lesser extent myocardial infarctions. At 40 to 50 years of age and above, more than 50% of patients had suffered from at least one such event, and many had experienced arterial thrombotic events despite regular plasma infusions every 2 to 3 weeks that supplements the missing plasma ADAMTS13. The article by van Dorland et al. (Haematologica 2019;104(10):2107-2115) and the ongoing Hereditary TTP Registry cohort study were recognized with the Günter Landbeck Excellence Award at the 50th Hemophilia Symposium in Hamburg in November 2019, the reason to present the Hereditary TTP Registry in more detail here.

Thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP; also known as Moschcowitz disease) is characterized by the concomitant occurrence of often severe thrombocytopenia, microangiopathic haemolytic anaemia and a variable degree of ischaemic organ damage, particularly affecting the brain, heart and kidneys. Acute TTP was almost universally fatal until the introduction of plasma therapy, which improved survival from <10% to 80-90%. However, patients who survive an acute episode are at high risk of relapse and of long-term morbidity. A timely diagnosis is vital but challenging, as TTP shares symptoms and clinical presentation with numerous conditions, including, for example, haemolytic uraemic syndrome and other thrombotic microangiopathies. The underlying pathophysiology is a severe deficiency of the activity of a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), the protease that cleaves von Willebrand factor (vWF) multimeric strings. Ultra-large vWF strings remain uncleaved after endothelial cell secretion and anchorage, bind to platelets and form microthrombi, leading to the clinical manifestations of TTP. Congenital TTP (Upshaw-Schulman syndrome) is the result of homozygous or compound heterozygous mutations in ADAMTS13, whereas acquired TTP is an autoimmune disorder caused by circulating anti-ADAMTS13 autoantibodies, which inhibit the enzyme or increase its clearance. Consequently, immunosuppressive drugs, such as corticosteroids and often rituximab, supplement plasma exchange therapy in patients with acquired TTP.

Consensus on the standardization of terminology in thrombotic thrombocytopenic purpura and related thrombotic microangiopathies

Essentials An international collaboration provides a consensus for clinical definitions. This concerns thrombotic microangiopathies and thrombotic thrombocytopenic purpura (TTP). The consensus defines diagnosis, disease monitoring and response to treatment. Requirements for ADAMTS-13 are given.

SUMMARY

Background Thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS) are two important acute conditions to diagnose. Thrombotic microangiopathy (TMA) is a broad pathophysiologic process that leads to microangiopathic hemolytic anemia and thrombocytopenia, and involves capillary and small-vessel platelet aggregates. The most common cause is disseminated intravascular coagulation, which may be differentiated by abnormal coagulation. Clinically, a number of conditions present with microangiopathic hemolytic anemia and thrombocytopenia, including cancer, infection, transplantation, drug use, autoimmune disease, and pre-eclampsia and hemolysis, elevated liver enzymes and low platelet count syndrome in pregnancy. Despite overlapping clinical presentations, TTP and HUS have distinct pathophysiologies and treatment pathways. Objectives To present a consensus document from an International Working Group on TTP and associated thrombotic microangiopathies (TMAs). Methods The International Working Group has proposed definitions and terminology based on published information and consensus-based recommendations. Conclusion The consensus aims to aid clinical decisions, but also future studies and trials, utilizing standardized definitions. It presents a classification of the causes of TMA, and criteria for clinical response, remission and relapse of congenital and immune-mediated TTP.

High prevalence of hereditary thrombotic thrombocytopenic purpura in central Norway: from clinical observation to evidence

Essentials The population prevalence of hereditary thrombotic thrombocytopenic purpura (TTP) is unknown. We studied the prevalence of hereditary TTP and population frequencies of two ADAMTS-13 mutations. A high frequency of hereditary TTP related to ADAMTS-13 mutation c.4143_4144dupA was found. Vicinity of ABO blood group and ADAMTS-13 loci may facilitate screening of ADAMTS-13 mutations.

SUMMARY

Background Hereditary thrombotic thrombocytopenic purpura (TTP) caused by ADAMTS-13 mutations is a rare, but serious condition. The prevalence is unknown, but it seems to be high in Norway. Objectives To identify all patients with hereditary TTP in central Norway and to investigate the prevalence of hereditary TTP and the population frequencies of two common ADAMTS-13 mutations. Patients/Methods Patients were identified in a cross-sectional study within the Central Norway Health Region by means of three different search strategies. Frequencies of ADAMTS-13 mutations, c.4143_4144dupA and c.3178 C>T (p.R1060W), were investigated in a population-based cohort (500 alleles) and in healthy blood donors (2104 alleles) by taking advantage of the close neighborhood of the ADAMTS-13 and ABO blood group gene loci. The observed prevalence of hereditary TTP was compared with the rates of ADAMTS-13 mutation carriers in different geographical regions. Results We identified 11 families with hereditary TTP in central Norway during the 10-year study period. The prevalence of hereditary TTP in central Norway was 16.7 × 10(-6) persons. The most prevalent mutation was c.4143_4144dupA, accounting for two-thirds of disease causing alleles among patients and having an allelic frequency of 0.33% in the central, 0.10% in the western, and 0.04% in the southeastern Norwegian population. The allelic frequency of c.3178 C>T (p.R1060W) in the population was even higher (0.3-1%), but this mutation was infrequent among patients, with no homozygous cases. Conclusions We found a high prevalence of hereditary TTP in central Norway and an apparently different penetrance of ADAMTS-13 mutations.

ADAMTS13 gene variants and function in women with preeclampsia: a population- based nested case- control study from the HUNT Study

INTRODUCTION

Known genetic variants with reference to preeclampsia only explain a proportion of the heritable contribution to the development of this condition. The association between preeclampsia and the risk of cardiovascular disease later in life has encouraged the study of genetic variants important in thrombosis and vascular inflammation also in relation to preeclampsia. The von Willebrand factor-cleaving protease, ADAMTS13, plays an important role in micro vascular thrombosis, and partial deficiencies of this enzyme have been observed in association with cardiovascular disease and preeclampsia. However, it remains unknown whether decreased ADAMTS13 levels represent a cause or an effect of the event in placental and cardiovascular disease.

METHODS

We studied the distribution of three functional genetic variants of ADAMTS13, c.1852C>G (rs28647808), c.4143_4144dupA (rs387906343), and c.3178C>T (rs142572218) in women with preeclampsia and their controls in a nested case-control study from the second Nord-Trøndelag Health Study (HUNT2). We also studied the association between ADAMTS13 activity and preeclampsia, in serum samples procured unrelated in time of the preeclamptic pregnancy.

RESULTS

No differences were observed in genotype, allele or haplotype frequencies of the different ADAMTS13 variants when comparing cases and controls, and no association to preeclampsia was found with lower levels of ADAMTS13 activity.

CONCLUSION

Our findings indicate that ADAMTS13 variants and ADAMTS13 activity do not contribute to an increased risk of preeclampsia in the general population.

Late onset and pregnancy-induced congenital thrombotic thrombocytopenic purpura

We report on our patient (case 2) who experienced a first acute episode of thrombotic thrombocytopenic purpura (TTP) at the age of 19 years during her first pregnancy in 1976 which ended in a spontaneous abortion in the 30th gestational week. Treatment with red blood cell concentrates was implemented and splenectomy was performed. After having suffered from several TTP episodes in 1977, possibly mitigated by acetylsalicylic acid therapy, an interruption and sterilization were performed in 1980 in her second pregnancy thereby avoiding another disease flare-up. Her elder sister (case 1) had been diagnosed with TTP in 1974, also during her first pregnancy. She died in 1977 during her second pregnancy from a second acute TTP episode.

DIAGNOSIS

In 2013 a severe ADAMTS13 deficiency of <10% without detectable ADAMTS13 inhibitor was repeatedly found. Investigation of the ADAMTS13 gene showed that the severe ADAMTS13 deficiency was caused by compound heterozygous ADAMTS13 mutations: a premature stop codon in exon 2 (p.Q44X), and a missense mutation in exon 24 (p.R1060W) associated with low but measurable ADAMTS13 activity.

CONCLUSION

Genetic analysis of the ADAMTS13 gene is important in TTP patients of all ages if an ADAMTS13 inhibitor has been excluded.