Child-onset and adolescent-onset acquired thrombotic thrombocytopenic purpura with severe ADAMTS13 deficiency: a cohort study of the French national registry for thrombotic microangiopathy.
Severe ADAMTS-13 deficiency was found in 60% of patients diagnosed with acute idiopathic TTP, but in none of 130 patients diagnosed with HUS or in any of the 14 patients with hematopoietic stem cell transplantation-associated TMA.
Agents targeting vascular endothelial growth factor (VEGF) have increasingly been used for the treatment of advanced malignancies, and have been found to induce renal thrombotic microangiopathy (TMA) and proteinuria.
ADAMTS13 activity is usually normal or modestly reduced (>20%) in other forms of thrombotic microangiopathy secondary to hematopoietic progenitor cell transplantation, infection, and disseminated malignancy or in hemolytic uremic syndrome.
This could lead to the earlier confirmation or rapid exclusion of TTP when ADAMTS13 testing is not avalilable, facilitating a more suitable therapy based on the aetiology of the TMA.
Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy disorder associated with congenital or acquired deficiency of the von Willebrand factor-cleaving protease, ADAMTS13.
For thrombotic microangiopathies (TMAs), the diagnosis of atypical hemolytic uremic syndrome (aHUS) is made by ruling out Shiga toxin-producing Escherichia coli (STEC)-associated HUS and ADAMTS13 activity-deficient thrombotic thrombocytopenic purpura (TTP), often using the exclusion criteria for secondary TMAs.
Direct VEGFA inhibition <i>via</i> antibody binding or VEGF trap (a soluble decoy receptor) is associated with renal-specific thrombotic microangiopathy (TMA).
Thrombotic microangiopathies can be associated with defective regulation of the AP (atypical hemolytic-uremic syndrome) or with inadequate cleavage by ADAMTS-13 of ULVWF multimeric strings secreted by/anchored to ECs (thrombotic thrombocytopenic purpura).
There were no mutations in factor H, factor I, or membrane cofactor protein of the complement alternative pathway, while plasma ADAMTS13 activity persisted and anti-ADAMTS13 antibodies were undetectable in patients with TMA.
To aid in the accurate diagnosis of TMA and other associated disorders, we have undertaken a review and provided a clear interpretation of some typical biomarkers including schistocytes, LDH and platelet count, coagulation profile and more specific indexes of ADAMTS13, complement profile, and the isolation of Shiga toxin-producing <i>Escherichia coli</i> (commonly referred to as STEC).
Bevacizumab, a monoclonal antibody against VEGF, is known to cause thrombotic microangiopathy (TMA), while tyrosine kinase inhibitors (TKIs) that block VEGF downstream are mainly associated with minimal change disease or focal segmental glomerulosclerosis.
Patients with thrombotic microangiopathies (TMA) associated with hematopoietic stem cell transplantation, neo-plasia and several drugs, usually have normal or only moderately reduced ADAMTS-13 activity, with the exception of ticlopidine-induced TMA.
Since TPE was effective and the ADAMTS13 assay revealed 55% activity in the absence of anti-ADAMTS13 IgG prior to initiation of therapy, a confident diagnosis of TMA caused by acute pancreatitis was made.
With this new knowledge and the findings of ADAMTS13 autoinhibitors or mutations in TTP, it is time to redefine aHUS as a disorder with propensity to the development of thrombotic microangiopathy due to defective regulation of the alternative complement pathway and TTP as a disorder with propensity to arteriolar and capillary thrombosis due to ADAMTS13 deficiency.
The study involved a prospective cohort of adult TTP patients with acquired severe ADAMTS-13 deficiency (< 10%) and included in the registry of the French Reference Center for Thrombotic Microangiopathies.
We conducted a propensity score (PS)-matched study of 186 adult patients included in the Harvard Thrombotic Microangiopathy (TMA) Research Collaborative registry who presented with TMA suggestive of TTP but an ADAMTS13 activity level of more than 10%.
Deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), a VWF-cleaving protease, is the key factor in the pathogenesis of thrombotic thrombocytopenic purpura (TTP), a life-threatening thrombotic microangiopathy.