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- Andersson, Nadine, et al.
(författare)
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Genetic screening of children with suspected inherited bleeding disorders
- 2020
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 26:2, s. 314-324
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Genetic screening using high-throughput DNA sequencing has become a tool in diagnosing patients with suspected inherited bleeding disorders (IBD). However, its usefulness and diagnostic efficacy in children is unclear.AIM: To evaluate the diagnostic efficacy of genetic screening for IBD in children and downstream further testing.METHODS: After informed consent, children (<18 years) with suspected IBD underwent genetic screening with 94 selected genes.RESULTS: A total of 68 heterozygous class 3-5 variants were detected in 30 children, 2.3 variants per patient. Directed specific functional testing was performed after genetic screening in a subset of patients. Adhering to the ACMG guidelines, the results of functional testing together with family history and previous publications classified three variants as likely disease causing (class 4) and two variants as disease causing (class 5), all in children with thrombocytopenia. The overall diagnostic rate was 16.7% (5/30). Children with thrombocytopenia had a significantly higher rate of significant genetic findings, 5/9 (55.6%) vs. 0/21 (0%; P = .0009).CONCLUSION: We conclude that performing genetic screening in children is an effective tool especially for children with inherited thrombocytopenia and has the possibility to diagnose platelet disorders adequately early in life. Children with bleeding diathesis, normal coagulation work-up and without thrombocytopenia are unlikely to be diagnosed by genetic screening. Ethical issues such as incidental findings, variants associated with cancer and the interpretation of the genetic results into clinical practice remain problematic.
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| 4. |
- Fager Ferrari, Marcus, et al.
(författare)
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A rare heterozygous variant in FGB (Fibrinogen Merivale) causing hypofibrinogenemia in a Swedish family
- 2020
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Ingår i: Blood Coagulation and Fibrinolysis. - 1473-5733. ; 31:7, s. 481-484
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Tidskriftsartikel (refereegranskat)abstract
- Fibrinogen is essential for normal hemostasis. Congenital fibrinogen disorders (afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia and hypodysfibrinogenemia), caused by pathogenic variants in the genes FGA, FGB and FGG, have the potential of causing bleeding diathesis and/or thrombotic events of variable severity. We describe a case of familial hypofibrinogenemia in a Swedish family. The proband is a 27-year-old woman, with a history of significant bleeding diathesis. She was diagnosed with moderate hypofibrinogenemia (0.8 g/l), and genetic screening identified a rare heterozygous missense variant in FGB (c.854G>A, p.Arg285His) (Fibrinogen Merivale) previously described in a New Zealand European family with symptomatic hypofibrinogenemia. The father, sister and brother of the proband also harbored the FGB variant, segregating with hypofibrinogenemia (0.9-1.2 g/l). The proband showed a more severe bleeding phenotype compared with her other hypofibrinogenemic family members; this was attributed to a concomitant platelet dysfunction, also present in her normofibrinogenemic mother.
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| 5. |
- Fager Ferrari, Marcus, et al.
(författare)
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Collagen remodelling and plasma ascorbic acid levels in patients suspected of inherited bleeding disorders harbouring germline variants in collagen‐related genes
- 2021
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 27:1, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Variants in collagen-related genes COL1A1, COL3A1, COL5A1 andCOL5A2 are associated with Ehlers-Danlos syndrome (EDS), a heterogeneous groupof connective tissue disorders strongly associated with increased bleeding. Of patientswith incompletely explained bleeding diathesis, a relatively high proportion were shown to harbour at least one heterozygous variant of unknown significance (VUS) in one of these genes, the vast majority without meeting the clinical criteria for EDS.AIM: To investigate the functional consequences of the identified variants by assessingthe formation and degradation of types I, III and V collagen, in addition to plasmalevels of ascorbic acid (AA).METHODS: A total of 31 patients harbouring at least one heterozygous VUS in COL1A1, COL3A1, COL5A1 or COL5A2 and 20 healthy controls were assessed using monoclonal antibodies targeting neo-epitopes specific for collagen formation and degradation. Plasma AA levels were measured in patients using high-performance liquid chromatography.RESULTS: Serum levels of C5M (degradation of type V collagen) were decreased inpatients compared with healthy controls (p = .033). No significant differences werefound in biomarkers for remodelling of types I and III collagen. A significant negativecorrelation between bleeding (ISTH-BAT score) and plasma AA levels was shown(r = −.42; r2 = .17; p = .020). Suboptimal or marginally deficient AA status was foundin 8/31 patients (26%).CONCLUSION: Functional investigations of collagen remodelling were not able to identify any clear associations between the identified variants and increased bleeding.The negative correlation between plasma AA levels and ISTH-BAT score motivatesfurther investigations.
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| 7. |
- Fager Ferrari, Marcus, et al.
(författare)
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Evaluation of the Sialidase Inhibitor Oseltamivir in GNE-associated Thrombocytopenia
- 2021
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Ingår i: Research and practice in thrombosis and haemostasis. - 2475-0379. ; 5:S2, s. 644-645
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Konferensbidrag (refereegranskat)abstract
- Background: GNE encodes UDP-N-acetyl-glucosamine-2-epimerase/N-acetylmannosamine kinase, the rate limiting enzyme of sialic acid biosynthesis. Biallelic variants in GNE have recently been associated with severe isolated macrothrombocytopenia, attributed to an increased clearance of desialylated platelets. Interestingly, treatment with the sialidase inhibitor oseltamivir has been reported to increase platelet counts in conditions such as immune thrombocytopenia (ITP) and influenza. We present a case of a 17-year-old boy (the proband) with severe congenital macrothrombocytopenia (platelet counts < 10 x 109/L). Whole genome sequencing revealed two previously undescribed compound heterozygous variants in GNE (c.416_426del, p.Ile139Argfs*4 and c.1352G>A, p.Arg451Gln). The proband was otherwise healthy, with no signs of GNE myopathy. Aims: To investigate the consequences of the identified variants in GNE and evaluate the effect of oseltamivir in GNE-associated thrombocytopenia. Methods: Sialylation of platelets, granulocytes, lymphocytes and monocytes was determined by flow cytometry in the proband and healthy controls (n = 5), using Sambucus nigra lectin (SNA) and Maackia amurensis lectin II (MAL II). Platelet sialylation was reassessed in the proband following treatment with oseltamivir (75 mg twice daily, off-label use). Informed consent was obtained from all participants. The study was approved by the regional ethical committee. Results: Sialylation of platelets and leukocytes was markedly decreased in the proband compared with the healthy controls, consistent with a deleterious effect of the compound heterozygous variants in GNE (Figure 1). Platelet sialylation was persistently decreased after 18 days of treatment with oseltamivir, and no clinically significant elevation of the platelet counts could be observed (Figure 1, Figure 2).
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| 8. |
- Fager Ferrari, Marcus
(författare)
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Genetic Screening in Patients Suspected of Inherited Bleeding Disorders
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inherited bleeding disorders constitute a heterogeneous group of genetic diseases, affecting virtually all major components of the hemostatic system. The diagnostics are potentially complex, and a high proportion of patients remain without a conclusive diagnosis following work-up. In recent years, advances in high-throughput DNA sequencing technologies have facilitated the use of genetic investigations in patients suspected of inherited bleeding disorders. Even though genetic investigations have contributed appreciably to the diagnostics, a considerable proportion of the genetic variants identified are still of uncertain significance. The overall aim of this thesis was to investigate the significance of selected genetic variants identified in patients suspected of inherited bleeding disorders, presenting with incompletely explained bleeding tendencies. In Paper I, the consequences of heterozygous variants in the genes UNC13D, STX11 and STXBP2 were investigated by functional methods. The results suggested an association between heterozygous variants in UNC13D, STX11 or STXBP2 and impaired platelet degranulation, possibly contributing to increased bleeding in affected patients. In Paper II, a rare variant in FGB was identified as the cause of familial hypofibrinogenemia following genetic and functional investigations. In Paper III, investigations using biomarkers specific for collagen formation and degradation were not able to verify any functional abnormalities hypothesized to result from heterozygous variants in COL1A1, COL3A1, COL5A1 or COL5A2. However, an interesting negative correlation between plasma ascorbic acid levels and the ISTH-BAT bleeding score was observed in the patients. In Paper IV, two previously undescribed variants in GNE were found to be causative of severe congenital macrothrombocytopenia when harbored in a compound heterozygous state, as a result of markedly decreased platelet sialylation. Treatment with the sialidase inhibitor oseltamivir did not prove to be effective for increasing the platelet counts. In summary, this thesis contributes to the continuously increasing knowledge of genetic variants associated with inherited bleeding disorders, required for adequately diagnosing a higher proportion of patients suffering from constitutionally increased bleeding.
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| 9. |
- Fager Ferrari, Marcus, et al.
(författare)
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Germline heterozygous variants in genes associated with familial hemophagocytic lymphohistiocytosis as a cause of increased bleeding
- 2018
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Ingår i: Platelets. - : Informa UK Limited. - 0953-7104 .- 1369-1635. ; 29:1, s. 56-64
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Tidskriftsartikel (refereegranskat)abstract
- Familial hemophagocytic lymphohistiocytosis (FHL) is caused by biallelic variants in genes regulating granule secretion in cytotoxic lymphocytes. In FHL3–5, the affected genes UNC13D, STX11 and STXBP2 have further been shown to regulate the secretion of platelet granules, giving rise to compromised platelet function. Therefore, we aimed to investigate platelet degranulation in patients heterozygous for variants in UNC13D, STX11 and STXBP2. During the work-up of patients referred to the Coagulation Unit, Skåne University Hospital, Malmö, Sweden and the Department of Hematology, Rigshospitalet, Copenhagen, Denmark due to bleeding tendencies, 12 patients harboring heterozygous variants in UNC13D, STX11 or STXBP2 were identified using targeted whole exome sequencing. Transmission electron microscopy (TEM) was used to assess the secretion of platelet dense granules following thrombin stimulation. Platelet degranulation, activation and aggregation were further assessed by flow cytometry (FC) and light transmission aggregometry (LTA) with lumi-aggregometry. In total, eight out of twelve (67%) patients showed impaired degranulation by at least one of the assays (TEM, FC and LTA). In the 12 patients, eight different heterozygous variants were identified. One variant was strongly associated with impaired degranulation, while four of the variants were associated with impaired granule secretion to a slightly lesser extent. One additional variant was found in six out of the twelve patients, and was associated with varying degrees of degranulation impairment. Accordingly, six out of the eight (75%) identified variants were associated with impaired platelet degranulation. Our results suggest that heterozygous variants in UNC13D, STX11 and STXBP2 are sufficient to cause platelet secretion defects resulting in increased bleeding.
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| 10. |
- Smolag Klosowska, Karolina, et al.
(författare)
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Severe Congenital Thrombocytopenia Characterized by Decreased Platelet Sialylation and Moderate Complement Activation Caused by Novel Compound Heterozygous Variants in GNE
- 2021
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Hereditary thrombocytopenias constitute a genetically heterogeneouscause of increased bleeding. We report a case of a 17-year-old boy suffering fromsevere macrothrombocytopenia throughout his life. Whole genome sequencing revealed the presence of two compound heterozygous variants in GNE encoding the enzyme UDP-N-acetyl-glucosamine-2-epimerase/N-acetylmannosamine kinase, crucial for sialic acid biosynthesis. Sialic acid is required for normal platelet life span, and biallelic variants in GNE have previously been associated with isolated macrothrombocytopenia. Furthermore, sialic acid constitutes a key ligand for complement factor H (FH), an important inhibitor of the complement system, protecting host cells fromindiscriminate attack.Methods: Sialic acid expression and FH binding to platelets and leukocytes wasevaluated by flow cytometry. The binding of FH to erythrocytes was assessed indirectlyby measuring the rate of complement mediated hemolysis. Complement activation wasdetermined by measuring levels of C3bBbP (alternative pathway), C4d (classical/lectinpathway) and soluble terminal complement complex assays.Results: The proband exhibited markedly decreased expression of sialic acid on platelets and leukocytes. Consequently, the binding of FH was strongly reduced and moderate activation of the alternative and classical/lectin complement pathways was observed, together with an increased rate of erythrocyte lysis.Conclusion: We report two previously undescribed variants in GNE causing severecongenital macrothrombocytopenia in a compound heterozygous state, as aconsequence of decreased platelet sialylation. The decreased sialylation of platelets, leukocytes and erythrocytes affects the binding of FH, leading to moderate complement activation and increased hemolysis.
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