Search

Congenital thrombotic thrombocytopenic purpura is an autosomal recessive inherited disease with a clinically heterogeneous course and an incompletely understood genotype-phenotype correlation. In 2006, the Hereditary TTP Registry started recruitment for a study which aimed to improve the understanding of this ultra-rare disease. The objective of this study is to present characteristics of the cohort until the end of 2017 and to explore the relationship between overt disease onset and ADAMTS13 activity with emphasis on the recurring ADAMTS13 c.4143&#95;4144dupA mutation. Diagnosis of congenital thrombotic thrombocytopenic purpura was confirmed by severely deficient ADAMTS13 activity (≤10% of normal) in the absence of a functional inhibitor and the presence of ADAMTS13 mutations on both alleles. By the end of 2017, 123 confirmed patients had been enrolled from Europe (n=55), Asia (n=52, 90% from Japan), the Americas (n=14), and Africa (n=2). First recognized disease manifestation occurred from around birth up to the age of 70 years. Of the 98 different ADAMTS13 mutations detected, c.4143&#95;4144dupA (exon 29; p.Glu1382Argfs*6) was the most frequent mutation, present on 60 of 246 alleles. We found a larger proportion of compound heterozygous than homozygous carriers of ADAMTS13 c.4143&#95;4144dupA with overt disease onset at < 3 months of age (50% vs 37%), despite the fact that ADAMTS13 activity was <1% in 18 of 20 homozygous, but in only 8 of 14 compound heterozygous carriers. An evaluation of overt disease onset in all patients with an available sensitive ADAMTS13 activity assay (n=97) shows that residual ADAMTS13 activity is not the only determinant of age at first disease manifestation. Registered at clinicaltrials.gov identifier NCT01257269 ., (Copyright© 2019 Ferrata Storti Foundation.)

Anti-ADAMTS13 autoantibodies are the main cause of acquired thrombotic thrombocytopenic purpura. Binding of these antibodies to ADAMTS13 eventually results in the formation of antigen-antibody immune complexes. Circulating ADAMTS13-specific immune complexes have been described in patients with acquired thrombotic thrombocytopenic purpura, although the prevalence and persistence of these immune complexes over time have hitherto remained elusive. Here, we analyzed a large cohort of patients with acquired thrombotic thrombocytopenic purpura for the presence of free and complexed anti-ADAMTS13 antibodies. In the acute phase (n=68), 100% of patients had free IgG antibodies and 97% had ADAMTS13-specific immune complexes. In remission (n=28), 75% of patients had free antibodies (mainly IgG) and 93% had ADAMTS13-specific immune complexes. Free antibodies were mainly of subclasses IgG1 and IgG4, whereas IgG4 was by far the most prevalent in ADAMTS13-specific immune complexes. Comparison of ADAMTS13 inhibitor and anti-ADAMTS13 IgG (total and subclasses) antibody titers in acute phase and in remission samples showed a statistically significant decrease in all parameters in remission. Although non-significant, a trend towards reduced or undetectable titers in remission was also observed for ADAMTS13-specific immune complexes of subclasses IgG1, IgG2 and IgG3. No such trend was discernible for IgG4; IgG4 immune complexes persisted over years, even in patients who had been treated with rituximab and who showed no features suggesting relapse.

Background: Severe ADAMTS13 deficiency is a critical component of the pathogenesis of idiopathic thrombotic thrombocytopenic purpura but is found only in about 60% of patients clinically diagnosed with this disease., Design and Methods: Over a period of 8 years and six episodes of thrombotic thrombocytopenic purpura we studied the evolution of the anti-ADAMTS13 antibody response in a patient using different ADAMTS13 assays and epitope mapping., Results: Anti-ADAMTS13 autoantibodies were found in all episodes but were inhibitory only in the last two episodes. In a flow-based assay, normal ADAMTS13 activity was found only during the first disease episode, while ADAMTS13 activity was normal using a static assay in episodes 1 and 3, and severely deficient in the last two episodes. Fluorescence evolution in a modified fluorescence resonance energy transfer assay using a von Willebrand factor A2 domain peptide substrate was linear in episodes 1, 5 and 6, but increased exponentially in episodes 3 and 4. Despite the variable functional characteristics of the anti-ADAMTS13 autoantibodies, their principal epitope was the ADAMTS13 spacer domain in all episodes., Conclusions: The patient is unique as he displayed features of maturation or shaping of the anti-ADAMTS13 autoantibody response during the course of multiple episodes of thrombotic thrombocytopenic purpura. Anti-ADAMTS13 autoantibodies may be important in vivo despite normal ADAMTS13 activity in routine assays. Consequently, treatment decisions should not be based solely on activity assay results.

Background and Objectives: The thrombotic thrombocytopenic purpura-hemolytic uremic syndromes (TTP-HUS) have diverse etiologies, clinical manifestations, and risk factors, but the events that may trigger acute episodes are often unclear. We describe the occurrence of TTP-HUS following pancreatitis and consider whether pancreatitis may be a triggering event for acute episodes of TTP-HUS., Design and Methods: We report on three patients from the Oklahoma Registry and two patients from Northwestern University who had an acute episode of TTP-HUS following pancreatitis. A systematic review of published case reports was performed to identify additional patients who had TTP-HUS following pancreatitis., Results: In each of our five patients there was an apparent etiology of alcoholism or common bile duct obstruction for the pancreatitis and no evidence of TTP-HUS when the pancreatitis was diagnosed. Two patients had severe ADAMTS13 deficiency with an inhibitor; in one of these patients TTP-HUS recurred following a subsequent recurrent episode of pancreatitis. The systematic review identified 16 additional patients who had TTP-HUS following pancreatitis; recurrent TTP-HUS occurred in three of these patients following a subsequent episode of recurrent pancreatitis. In all 21 patients, the interval between the diagnosis of pancreatitis and TTP-HUS was short (1-13 days; median, 3 days). The three Oklahoma patients represent approximately 1% of the 356 patients in the Registry., Interpretation and Conclusions: These observations suggest that in some patients pancreatitis, a disorder that results in an intense systemic inflammatory response, may be a triggering event for acute episodes of TTP-HUS.

Background and Objectives: Acquired thrombotic thrombocytopenic purpura (TTP) is often due to autoantibodies inhibiting ADAMTS-13 activity resulting in impaired processing of very large von Willebrand factor multimers. TTP usually presents with an acute onset and a fulminant, sometimes fatal course. With appropriate treatment including plasma exchange, and fresh frozen plasma replacement, often supplemented by immuno-suppressive therapy, the acute episode generally resolves within days to weeks., Design and Methods: We describe the clinical course of 3 patients with acquired TTP. One was refractory to PE, the other 2 relapsed after this treatment. All three were treated with splenectomy. ADAMTS-13 activity and inhibitor levels were monitored., Results: ADAMTS-13 activity was initially < 5% in all 3 patients. After splenectomy the inhibitor against ADAMTS-13 disappeared rapidly in 2 patients and there was full recovery of ADAMTS-13 activity in all 3 patients., Interpretation and Conclusions: Splenectomy, by eliminating a source of pathogenic autoantibody production, can be a successful treatment for patients with relapsing or plasma-refractory acquired TTP due to autoantibody-mediated ADAMTS-13 deficiency.