György Sinkovits1, Edina Szabó1, Dorottya Csuka1, Ágnes Szilágyi1, Johanna A Kremer Hovinga2, Maria Szczepanska3, Katalin Rázsó4, Marienn Réti5, Zoltán Prohászka1

1Research Laboratory, 3rd Department of Internal Medicine and MTA-SE Research Group of Immunology and Hematology, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary; 2Department of Hematology and Central Hematology Laboratory, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; 3Department of Pediatrics SMDZ in Zabrze, SUM in Katowice, Zabrze, Poland; 4Division of Hematology, Department of Internal Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; 5Dept. of Hematology and Stem Cell Transplantation, St. László Hospital Campus, South-Pest Hospital Center, Institute of Hematology and Infectology, Budapest, Hungary

Introduction

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy, characterized by the severe deficiency of ADAMTS13, which is responsible for cleaving ultra-large von Willebrand factor multimers. ADAMTS13 deficiency is caused by anti-ADAMTS13 autoantibodies in the acquired form of the disease, or by bi-allelic (homozygous or compound heterozygous) ADAMTS13 mutations in its hereditary form.

The c.3178C>T (p.R1060W) mutation is the second most frequent ADAMTS13 mutation in European TTP patients [1], which was described predominantly in adult-onset hereditary TTP cases [1-4], and is often associated with first disease manifestation in pregnancy [2-4].

Interestingly, this pathogenic variation was reported to cause ADAMTS13 deficiency in heterozygous form, in the absence of other mutations [3,4].

In some of these cases, anti-ADAMTS13 antibodies were detectable [3], whereas the exact cause of ADAMTS13 deficiency is unknown in other cases.

The main parameters of the c.3178C>T mutation are described in Table 1.

1: Reference ID of the single nucleotide polymorphism (SNP) according to dbSNP

(URL: www.ncbi.nlm.nih.gov/projects/SNP/).
2: Minor allele frequency based on 1000Genomes Project phase 1 genotype data of 1094 worldwide individuals, as reported by dbSNP, and on the genotype data of 4300 European Americans according to ESP (Exome Sequencing Project ), respectively.
Abbreviations: Tsp-7: 7th thrombospondin-1-like domain.

Objectives

In order

  • to better understand the mechanism how c.3178C>T (p.R1060W) can lead to ADAMTS13 deficiency alone, in the absence of other mutations, and
  • to examine its association with anti-ADAMTS13 antibodies,

we investigated

  • the prevalence of the c.3178C>T mutation in a cohort of hereditary and acquired TTP patients, and
  • its association with clinical parameters, other mutations, and antibody levels.

Patients and methods

Our cohort consisted of 8 hereditary and 146 acquired TTP patients.

In hereditary TTP patients, the full ADAMTS13 gene (29 exons) was analyzed by Sanger sequencing.

Exon 24 (containing c.3178) was selectively analyzed in acquired TTP patients and two healthy relatives of a hereditary patient carrying the c.3178C>T mutation by Sanger sequencing.

Results

One (HUN994) out of the two adult-onset hereditary TTP patients in our cohort was found to carry the c.3178C>T mutation in compound heterozygous form together with the common ADAMTS13 c.4143-4144insA mutation.

No other hereditary or acquired TTP patient carried the c.3178C>T mutation, as shown in Table 2.

Clinical parameters and ADAMTS13 data (activity, antibodies, mutations and polymorphisms) of the only patient carrying the c.3178C>T mutation (HUN994) are summarized in Table 3. Neither of the patient’s relatives was found to carry the c.3178C>T mutation. (Figure 2.)

Conclusions

The c.3178C>T mutation was present in one adult-onset hereditary TTP patient in our cohort

In contrast with previous studies, the c.3178C>T mutation was neither found alone, in the absence of another mutation, nor in patients with detectable anti-ADAMTS13 antibodies in our TTP cohort.

REFERENCES

  1. van Dorland HA et al. The International Hereditary Thrombotic Thrombocytopenic Purpura Registry: Key findings at enrolment until 2017. Haematologica, 2019
  2. Tao Z et al. Novel ADAMTS-13 mutations in an adult with delayed onset thrombotic thrombocytopenic purpura. J Thromb Haemost, 2006
  3. Camilleri RS et al. Prevalence of the ADAMTS-13 missense mutation R1060W in late onset adult thrombotic thrombocytopenic purpura. J Thromb Haemost, 2008
  4. Moatti-Cohen M et al. Unexpected frequency of Upshaw-Schulman syndrome in pregnancy-onset thrombotic thrombocytopenic purpura. Blood, 2012

This work was supported by the
ÚNKP-18-3 New National Excellence Program of the
Hungarian Ministry of Human Capacities.