Background: Thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy, characterised by thrombocytopenia, haemolytic anemia and possible organ damage. The disease is caused by a severely reduced activity of von Willebrand factor-cleaving protease ADAMTS13. This is due to the presence of an inhibitory autoantibody in the acquired form or to mutations in the ADAMTS13 gene in the rare inherited form.

Aims: In July 2020, a 20 weeks pregnant 31-year-old woman presented with general discomfort.

Methods: Laboratory investigations were suggestive for TTP with severe thrombocytopenia and haemolytic anemia with presence of schistocytes.

Results: ADAMTS13 activity was 3%, confirming TTP. Treatment with daily plasma exchange (PEX), caplacizumab and corticosteroids showed rapid normalization of laboratory and clinical parameters. PEX could be stopped after 5 days. From week 2, rituximab was administered once weekly for 4 weeks. Unfortunately, the baby deceased in utero at week 22 of gestation.
ADAMTS13 autoantibodies could not be identified, neither by Bethesda assay, nor by direct antibody ELISA. ADAMTS13 remained low during the next 2 months, therefore caplacizumab was continued. After 2 months, treatment was discontinued due to reimbursement modalities.
One week later, the patient relapsed clinically. Treatment with PEX, caplacizumab and corticosteroids was restarted. Shortly thereafter, results of the genetic analyses showed two mutations in the ADAMTS13 gene: c.3179C>T p.(Arg1060Trp), associated with late onset congenital TTP (cTTP), and c.84G>A p.(Trp28*), a possible novel mutation linked to cTTP. Genetic analysis in the parents confirmed our patient as compound heterozygous. Therapy was switched to 2-weekly fresh frozen plasma administration. Today, no relapse occurred and interval of infusion is extended to a 3-weekly regimen.

Conclusions: In conclusion, we suggest that pregnant women presenting with TTP should be screened for inherited TTP, even in the absence of a history of TTP-like symptoms. Our experience demonstrates that good clinical responses can be obtained with caplacizumab in cTTP.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/ttp-during-pregnancy-acquired-or-late-onset-congenital-a-diagnostic-challenge/