A Unique Case Involving a Female Patient with Upshaw-Schulman Syndrome: Low Titers of Antibodies against ADAMTS13 prior to Pregnancy Disappeared after Successful Delivery

Success and limitations of plasma treatment in pregnant women with congenital thrombotic thrombocytopenic purpura

BACKGROUND

Congenital thrombotic thrombocytopenic purpura (cTTP), otherwise known as Upshaw-Schulman syndrome, is an extremely rare hereditary disease. Pregnancy is identified as a trigger for TTP episodes in patients with cTTP.

OBJECTIVES

To investigate the ideal management of pregnant patients with cTTP.

PATIENTS/METHODS

We identified 21 patients with a reproductive history (38 pregnancies) in a Japanese cTTP registry. Fetal outcomes were compared between two groups: group 1 (n = 12), pregnancy after diagnosis of confirmed cTTP by ADAMTS13 gene analysis; and group 2 (n = 26), pregnancy before diagnosis of confirmed cTTP.

RESULTS

In group 1, ADAMTS13 activity was closely monitored until delivery in most cases. Among 10 pregnancies in group 1, prophylactic fresh frozen plasma (FFP) infusions during pregnancy were performed to replenish ADAMTS13. In group 2, prophylactic FFP infusions were not administrated in 23 pregnancies and FFP test infusions were performed in only three pregnancies. The live birth rate of group 1 was significantly higher than that of group 2 (91.7% vs 50.0%, respectively, P = .027). The fetal survival rates of women without FFP infusions were dramatically decreased after 20 weeks of gestation. The FFP infusion dosage in group 1 was generally higher than 5 mL/kg/wk by 20 weeks of gestation.

CONCLUSIONS

Our results indicate that FFP infusions of more than 5 mL/kg/wk should be initiated as soon as patients become pregnant. However, even with these infusions, patients with repeated TTP episodes before pregnancy might have difficulty giving birth successfully. Recombinant ADAMTS13 products might be new treatment options for pregnant patients with cTTP.

Anti-ADAMTS13 Antibodies and a Novel Heterozygous p.R1177Q Mutation in a Case of Pregnancy-Onset Immune-Mediated Thrombotic Thrombocytopenic Purpura

In this study, we investigated a case of pregnancy-onset thrombotic thrombocytopenic purpura (TTP). The patient had severely decreased ADAMTS13 ( ad isintegrin a nd m etalloprotease with t hrombo s pondin type 1 motif, member 13) activity levels during acute phase and the presence of inhibitory anti-ADAMTS13 autoantibodies was demonstrated, which led to the diagnosis of immune-mediated TTP. However, ADAMTS13 activity was only mildly restored during remission, although inhibitory anti-ADAMTS13 antibodies were no longer detected. We hypothesized that genetic abnormalities could account for this discrepancy between ADAMTS13 activity and antigen. Genetic analysis revealed the presence of two heterozygous substitutions on the same allele: a single nucleotide polymorphism (SNP) c.2699C > T (p.A900V), located in the beginning of the T5 domain, and a mutation c.3530G > A (p.R1177Q) located in the third linker region of ADAMTS13. In vitro testing of those substitutions by expression of recombinant proteins revealed a normal secretion but a reduced ADAMTS13 activity by the novel p.R1177Q mutation, which could partially explain the subnormal activity levels found during remission. Although changes in the linker region might induce conformational changes in ADAMTS13, the p.R1177Q mutation in the third linker region of ADAMTS13 did not expose a cryptic epitope in the metalloprotease domain. In conclusion, we report on an immune-mediated pregnancy-onset TTP patient who had inhibitory anti-ADAMTS13 autoantibodies during acute phase, but not during remission. Genetic analysis confirmed the diagnosis of immune-mediated TTP and revealed the novel p.R1177Q mutation which mildly impaired ADAMTS13 activity.