Follow-up Groningen antithrombin study

Antithrombin deficiency is a rare autosomal dominant coagulation disorder. The
prevalence of heterozygous antithrombin deficiency is estimated to be
approximately 1 in 500 to 1 in 5,000. Diagnosis is often made when patients
present early in life with one or more unexplained venous thromboembolisms
(VTE). The annual incidence of VTE recurrence in antithrombin deficiency is 10%
[1], and for antithrombin-deficient family members, it is 1.94% [2].

Antithrombin deficiency can be classified into different types. Type 1 is
characterized by a lack of circulating antithrombin proteins, while type 2 is
characterized by a functional disorder of the translated antithrombin protein.
The second type is further subdivided based on the specific position of the
mutation in 2RE (reactive site), 2HBS (heparin binding site), and 2PE
(pleiotropic effects). These subdivisions are of clinical significance because
the risks of VTE vary by (sub)type [3].

The antithrombin protein is encoded by the SERPINC1 gene. In the literature,
more than 250 different mutations in this gene have been described, mainly
heterozygous, as homozygous mutations are lethal in utero
[http://www.hgmd.cf.ac.uk/ac/;
https://www.imperial.ac.uk/immunology-inflammation/research/haematology/haemosta
sis-and-thrombosis/database/]. [3] The degree of prothromboticity of each
mutation is largely unknown. The relationship between genotype and phenotype is
mostly supported by antigen and activity measurements, not by cohort studies or
functional studies. Prediction programs are not consistent in predicting the
clinical consequences of mutations. Therefore, it is currently challenging to
determine the exact risks associated with each mutation.

In the GRAS study, which ran from 2013 to 2015 and is the predecessor to this
study, DNA testing was conducted in 81 individuals from a total of fifteen
families known at the UMCG [4]. In three families, mutations could not be
identified using the DNA techniques available at the time, despite strong
suspicions of a SERPINC1 mutation based on antithrombin antigen levels and
activity measurements. All three families had type 1 deficiency. The majority
of mutations leading to type 1 deficiency are point mutations and smaller and
larger insertions and deletions. Recent research on antithrombin deficiency and
other conditions suggests that (deep) intronic mutations may be a possible
cause [5-9].

Since the completion of the GRAS study, new DNA testing techniques have become
available, particularly whole-exome sequencing (WES) and whole-genome
sequencing (WGS). WGS, in particular, offers the opportunity to examine
relevant parts of the DNA for mutations that were not covered by the techniques
used from 2013 to 2015. [5, 6]

Referenties
1. Brouwer, J. L., Lijfering, W. M., Ten Kate, M. K., Kluin-Nelemans, H. C.,
Veeger, N. J., & van der Meer, J. (2009). High long-term absolute risk of
recurrent venous thromboembolism in patients with hereditary deficiencies of
protein S, protein C or antithrombin. Thrombosis and haemostasis, 101(1), 93-99.
2. Brouwer, J. L., Veeger, N. J., Kluin-Nelemans, H. C., & van der Meer, J.
(2006). The pathogenesis of venous thromboembolism: evidence for multiple
interrelated causes. Annals of internal medicine, 145(11), 807-815.
https://doi.org/10.7326/0003-4819-145-11-200612050-00005
3. Luxembourg, B., Delev, D., Geisen, C., Spannagl, M., Krause, M., Miesbach,
W., Heller, C., Bergmann, F., Schmeink, U., Grossmann, R., Lindhoff-Last, E.,
Seifried, E., Oldenburg, J., & Pavlova, A. (2011). Molecular basis of
antithrombin deficiency. Thrombosis and haemostasis, 105(4), 635-646.
https://doi.org/10.1160/TH10-08-0538
4. Mulder, R., Croles, F. N., Mulder, A. B., Huntington, J. A., Meijer, K., &
Lukens, M. V. (2017). SERPINC1 gene mutations in antithrombin deficiency.
British journal of haematology, 178(2), 279-285.
https://doi.org/10.1111/bjh.14658
5. de la Morena-Barrio, B., Stephens, J., de la Morena-Barrio, M. E.,
Stefanucci, L., Padilla, J., Miñano, A., Gleadall, N., García, J. L., López-
Fernández, M. F., Morange, P. E., Puurunen, M., Undas, A., Vidal, F., Raymond,
F. L., Vicente, V., Ouwehand, W. H., Corral, J., Sanchis-Juan, A., & NIHR
BioResource (2022). Long-Read Sequencing Identifies the First Retrotransposon
Insertion and Resolves Structural Variants Causing Antithrombin Deficiency.
Thrombosis and haemostasis, 122(8), 1369-1378.
https://doi.org/10.1055/s-0042-1749345
6. de la Morena-Barrio, M. E., Suchon, P., Jacobsen, E. M., Iversen, N.,
Miñano, A., de la Morena-Barrio, B., Bravo-Pérez, C., Padilla, J., Cifuentes,
R., Asenjo, S., Deleuze, J. F., Trégouët, D. A., Lozano, M. L., Vicente, V.,
Sandset, P. M., Morange, P. E., & Corral, J. (2022). Two SERPINC1 variants
affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by
functional assays. Blood, 140(2), 140-151.
https://doi.org/10.1182/blood.2021014708
7. Wójcik, M., de la Morena-Barrio, M. E., Michalik, J., Wypasek, E., Kopytek,
M., Corral, J., & Undas, A. (2019). A series of 10 Polish patients with
thromboembolic events and antithrombin deficiency: two new c.1154-1 G>C and
c.1219-534 A>G SERPINC1 gene splicing mutations. Blood coagulation &
fibrinolysis : an international journal in haemostasis and thrombosis, 30(5),
193-198. https://doi.org/10.1097/MBC.0000000000000816
8. de la Morena-Barrio, M. E., López-Gálvez, R., Martínez-Martínez, I., Asenjo,
S., Sevivas, T. S., López, M. F., Wypasek, E., Entrena, L., Vicente, V., &
Corral, J. (2017). Defects of splicing in antithrombin deficiency. Research and
practice in thrombosis and haemostasis, 1(2), 216-222.
https://doi.org/10.1002/rth2.12025
9. Vatsiou, S., Zamanakou, M., Loules, G., Psarros, F., Parsopoulou, F., Csuka,
D., Valerieva, A., Staevska, M., Porebski, G., Obtulowicz, K., Magerl, M.,
Maurer, M., Speletas, M., Farkas, H., & Germenis, A. E. (2020). A novel deep
intronic SERPING1 variant as a cause of hereditary angioedema due to
C1-inhibitor deficiency. Allergology international : official journal of the
Japanese Society of Allergology, 69(3), 443-449.
https://doi.org/10.1016/j.alit.2019.12.009
10. Vaz-Drago, R., Custódio, N., & Carmo-Fonseca, M. (2017). Deep intronic
mutations and human disease. Human genetics, 136(9), 1093-1111.
https://doi.org/10.1007/s00439-017-1809-4
11. Catania, A., Ardissone, A., Verrigni, D., Legati, A., Reyes, A., Lamantea,
E., Diodato, D., Tonduti, D., Imperatore, V., Pinto, A. M., Moroni, I.,
Bertini, E., Robinson, A., Carrozzo, R., Zeviani, M., & Ghezzi, D. (2018).
Compound heterozygous missense and deep intronic variants in NDUFAF6 unraveled
by exome sequencing and mRNA analysis. Journal of human genetics, 63(5), 563-
568. https://doi.org/10.1038/s10038-018-0423-1

The purpose of this study is to identify a pathogenic or likely pathogenic
variant in unresolved families with antithrombin deficiency.

This is a genetic mutation identification study based on a family cohort.

Minimal risk and minimal burden for the participants: only a venapuncture.