A role for tissue plasminogen activator in thrombotic thrombocytopenic purpura

An ADAMTS13 mutation that causes hereditary thrombotic thrombocytopenic purpura: a case report and literature review

Background

Mutations in the ADAMTS13 gene can lead to an ADAMTS13 enzyme deficiency, which is related to Upshaw–Schulman syndrome (USS). USS is a common type of thrombotic thrombocytopenic purpura (TTP). Here we present a very rare case of TTP caused by 2 mutations in the ADAMTS13 gene. Besides, we reviewed and summarized previous pathogenic ADAMTS13 gene mutations associated with the TTP.

Case presentation

A 10-year-old female was admitted to the Third Xiangya Hospital of Central South University after experiencing discontinuous thrombocytopenia for 8 years, abnormal renal function for more than 2 years, cough for more than 10 days, and weakness of the left limb for 3 days. Gene sequencing shows the patient’s ADAMTS13 gene contains compound heterozygous nucleotide variations: c.1335delC (p. Phe445LeufsTer52) is a frameshift variation inherited from her father and c.2130C > G (p. Cys710Trp) is a missense variation inherited from her mother. The final diagnosis was USS.

Conclusions

Our study reports a very rare genetic TTP case caused by two compound heterozygous variants in the ADAMTS13 gene. The effect of these two mutations on the secretion of ADAMTS13 requires further in vitro experiments to confirm.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01099-3.

ADAMTS13 Secretion and Residual Activity among Patients with Congenital Thrombotic Thrombocytopenic Purpura with and without Renal Impairment

BACKGROUND AND OBJECTIVES

Acute renal impairment is observed in 11%-23% of patients with congenital thrombotic thrombocytopenic purpura (TTP) and deficiency of a disintegrin and metalloprotease with thrombospondin motifs 13 (ADAMTS13, a metalloprotease that cleaves von Willebrand factor [VWF] multimers), a substantial percentage of whom develop CKD during follow-up.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Here we investigated whether, in 18 patients with congenital recruited from 1996 to 2013 who fulfilled inclusion criteria, acute renal involvement occurred during bouts segregated with lower secretion and activity levels of ADAMTS13 mutants. We performed expression studies and a sensitive recombinant VWF (rVWF) A1-A2-A3 cleavage test (detection limit, 0.78% of normal ADAMTS13 activity).

RESULTS

A higher risk of acute renal impairment during bouts was observed in patients with childhood (<18 years) onset (odds ratio [OR], 24.6 [95% confidence interval (CI), 1.11 to 542.44]) or a relapsing (≥1 episode per year) disease (OR, 54.6 [95% CI, 2.25 to 1326.28]) than in patients with adulthood onset or long-lasting remission, respectively. Whatever the age at onset, patients with acute renal impairment had mutations different from those in patients without renal involvement. Moreover, mutations in patients with acute renal impairment compared with those in patients without renal involvement caused lower in vitro rADAMTS13 secretion (1.33% versus 12.5%; P<0.001) and residual activity (0.11% versus 3.47%; P=0.003). rADAMTS13 secretion ≤3.75% and residual activity ≤0.4% best discriminated patients with renal impairment (receiver-operating characteristic curve sensitivity, 100% and 100%; specificity, 100% and 83.3%, respectively; logistic regression OR, 325 [95% CI, 6 to 18339] and 91.7 [95% CI, 3.2 to 2623.5], respectively). All mutations found in patients with childhood onset or relapsing disease were associated with acute renal impairment during bouts, confirming the link between acute renal impairment and early onset or a relapsing course. ADAMTS13 activity levels in vivo, measured in patients' serum by rVWF A1-A2-A3 cleavage test, correlated with in vitro rADAMTS13 mutant activity (r=0.95; P<0.001).

CONCLUSIONS

In congenital TTP, renal impairment and relapsing disease might be predicted by measurements of in vitro rADAMTS13 secretion and activity levels and in vivo serum ADAMTS13 activity.