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Case Reports
. 2023 Apr 11;18(1):74.
doi: 10.1186/s13023-023-02675-9.

Novel SLFN14 mutation associated with macrothrombocytopenia in a patient with severe haemorrhagic syndrome

Dmitrii Polokhov  1 , Daria Fedorova  2 , Anastasiya Ignatova  2 , Evgeniya Ponomarenko  2 , Elena Rashevskaya  2 , Alexey Martyanov  2 , Nadezhda Podoplelova  2 , Maxim Aleksenko  2 , Irina Mersiyanova  2 , Elena Seregina  2 , Aleksandr Poletaev  2 , Ekaterina Truchina  2 , Elena Raykina  2 , Svetlana Plyasunova  2 , Galina Novichkova  2 , Pavel Zharkov  2 , Mikhail Panteleev  2   3   4
Affiliations
Case Reports

Novel SLFN14 mutation associated with macrothrombocytopenia in a patient with severe haemorrhagic syndrome

Dmitrii Polokhov et al. Orphanet J Rare Dis. .

Abstract

Background: Platelet-type bleeding disorder 20 (BDPLT20), as known as SLFN14-related thrombocytopenia, is a rare inherited thrombocytopenia (IT). Previously, only 5 heterozygous missense mutations in the SLFN14 gene have been reported.

Methods: A comprehensive clinical and laboratory examination of a 17-year-old female patient with macrothrombocytopenia and severe mucocutaneous bleeding was performed. Examination was carried out using standardized questionnaires to assess bleeding, high-throughput sequencing (Next Generation Sequencing), optical and fluorescence microscopy, flow cytometry with activation and analysis of intracellular calcium signaling of platelets, light transmission aggregometry and thrombus growth in the flow chamber.

Results: Analysis of the patient's genotype revealed a previously undescribed c.655 A > G (p.K219E) variant in the hotspot of the SLFN14 gene. Immunofluorescence and brightfield examination of platelets in the smear showed heterogeneity in cells size, including giant forms over 10 μm (normal size 1-5) in diameter, with vacuolization and diffuse distribution of β1-tubulin and CD63. Activated platelets showed impaired contraction and shedding/internalization of GPIb. GP IIb/IIIa clustering was increased at rest and attenuated upon activation. Intracellular signalling study revealed impaired calcium mobilization upon TRAP 35.97 nM (reference range 180 ± 44) and CRP-XL 10.08 nM (56 ± 30) stimulation. Aggregation with ADP, collagen, TRAP, arachidonic acid and epinephrine was impaired in light transmission aggregometry; agglutination with ristocetin persisted. In the flow chamber with a shear rate of 400 s-1 platelet adhesion to collagen and clot growth were impaired.

Conclusion: The revealed disorders of phenotype, cytoskeleton and intracellular signaling explain the nature of SLFN14 platelet dysfunction and the patient's severe hemorrhagic syndrome.

Keywords: Bleeding; Inherited thrombocytopenia; Platelet dysfunction; Platelet function tests; SLFN14; macrothrombocytopenia.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
SLFN14 mutation and optical microscopy of platelets (×1000 magnification). Panel A shows affected persons (shaded). The # sign marks the patient, and the arrow indicates the change in nucleotides in the chromatogram. Panel B shows a blood smear from a healthy volunteer with normal platelets. Panels C and D show the patient’s platelets heterogeneous in size with large vacuolar inclusions.
Fig. 2
Fig. 2
Immunofluorescence microscopy of platelets (×1000 magnification). Panel A shows the normal distribution of CD63 dense granules from a healthy volunteer, panel B shows a diffuse distribution of CD63 in the patient’s platelets. Panel C shows normal expression of β1-tubulin, panel D shows diffuse distribution of β1-tubulin in the patient’s platelets.
Fig. 3
Fig. 3
Light transmission aggregometry and growth of thrombi in the flow chamber. Panel A shows platelet aggregation curves from a healthy volunteer. Panel B shows the patient’s aggregation alteration with all agonists except agglutination/aggregation with ristocetin. The number of thrombus foci was reduced in the patient compared to the control (panels D and C, respectively, microphotographs at ×20 magnification). The length of the thrombi in the patient was comparable to the control (panels F and E, respectively, microphotographs at ×100 magnification).
See this image and copyright information in PMC

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