Platelet-type Bleeding Disorder 20 (BDPLT20) — Comprehensive Research Report

1. Disease Information

Overview: Platelet-type Bleeding Disorder 20 (BDPLT20), also known as SLFN14-related thrombocytopenia, is a rare autosomal dominant inherited platelet disorder characterized by moderate thrombocytopenia (often with macrothrombocytes/enlarged platelets), impaired platelet secretion (particularly ATP release from dense granules), and a lifelong mucocutaneous bleeding tendency. It was first delineated as a distinct clinical entity by Fletcher et al. in 2015, who identified heterozygous missense mutations in the SLFN14 (Schlafen family member 14) gene as the molecular cause (JCI, PMID: 26280575).

Key Identifiers: - OMIM: #616913 — BLEEDING DISORDER, PLATELET-TYPE, 20; BDPLT20 (OMIM entry) - Gene locus (OMIM): 614958 — SCHLAFEN FAMILY, MEMBER 14; SLFN14 (OMIM entry) - HGNC: SLFN14, HGNC:32689 - MONDO: MONDO:0014830 (ClinGen curation page) - MedGen: C4310797 (NCBI MedGen) - Orphanet: ORPHA:466806 — SLFN14-related thrombocytopenia (Orphanet gene page) - NCBI GTR:* Genetic Testing Registry entry - Chromosomal location: 17q12

Synonyms: SLFN14-related thrombocytopenia; SLFN14-related macrothrombocytopenia; Inherited thrombocytopenia due to SLFN14 mutation.

Evidence basis: Nearly all published knowledge derives from individual patient/family case series and case reports (aggregated across roughly a dozen kindreds worldwide identified via next-generation sequencing in bleeding-disorder cohorts such as the UK GAPP [Genotyping and Phenotyping of Platelets] study), supplemented by mechanistic cell-line and mouse-model studies. There is no large-scale disease registry or population-level epidemiological dataset — this is characteristic of an ultra-rare monogenic platelet disorder.

2. Etiology

Disease Causal Factor: BDPLT20 is caused by heterozygous, dominantly acting missense (and at least one frameshift) mutations in SLFN14, which encodes an RNA endoribonuclease. This is a purely genetic/monogenic disorder — no environmental or infectious causal factors are described.

Genetic Risk Factors: - Fletcher et al. (2015) identified three heterozygous missense mutations — p.K218E, p.K219N, p.V220D — clustered within an ATPase-associated-with-diverse-cellular-activities (AAA) GTP/ATP-binding domain, in 12 patients from 3 unrelated families (PMID: 26280575). - Marconi et al. (2016) reported an additional heterozygous missense mutation in an Italian family — Thromb Haemost. 2016;115(5):1076-9 (PMID: 26769223). - A p.R223W substitution in the AAA domain, near previously reported residues, has also been described. - A novel c.1766T>C (p.L589S) variant in the helicase domain was reported in 2025 in twin brothers with severe thrombocytopenia and abnormal megakaryocyte maturation — notably, the variant showed incomplete penetrance: "the mother and maternal grandmother showed no abnormal phenotypes" despite carrying the variant (EJHaem 2025, PMID: 40521396). - A frameshift variant, T853fs, was identified in the helicase domain in patients with inherited macrothrombocytopenia, distinct in mechanism from the AAA-domain missense variants (Mol Ther Nucleic Acids 2025, PMID: 40510593). - A novel variant was reported in a 17-year-old female with severe macrothrombocytopenia and giant platelets (>10 μm) (Orphanet J Rare Dis 2023, PMID: 37041648). - Maternal gonosomal (germline) mosaicism has been documented as a mechanism of transmission in at least one family, relevant to genetic counseling and recurrence-risk estimation (Br J Haematol 2022, PMID: 36237120). - Across the literature, five heterozygous single-nucleotide substitutions have been reported, producing four distinct amino-acid changes (p.K218E, p.K219N, p.V220D, p.R223W), plus the more recently identified helicase-domain missense and frameshift variants.

Risk Factor Databases: Because this is a single-gene autosomal dominant disorder with no described modifier genes, environmental risk factors, or GWAS-identified susceptibility loci, the standard PheGenI/GWAS Catalog/CTD resources return no relevant hits — risk is essentially binary (carrying a pathogenic SLFN14 variant vs. not), modulated somewhat by variant location (AAA-ATPase domain vs. helicase domain) and possibly by mosaicism/penetrance effects.

Protective Factors: None reported in the literature; there are no known protective genetic variants or environmental protective factors specific to BDPLT20.

Gene-Environment Interactions: Not described; this is a purely cell-intrinsic, monogenic disorder of megakaryocyte/platelet biology.

3. Phenotypes

Clinical/hemorrhagic phenotypes (symptoms and signs)

Based on the original description of a 9-member, 3-generation family (proband: 31-year-old woman) and subsequent case series:

Laboratory/hematologic abnormalities

• Thrombocytopenia (HP:0001873) — typically "moderate" (platelet counts variably reduced, not typically in the severe <20×10⁹/L range in most reported families, though severe cases have been described in twin patients with the L589S variant)
• Macrothrombocytes / enlarged platelets (HP:0011877, Abnormal platelet volume) — a hallmark feature; one case report described "heterogeneity in cell size, including giant forms over 10 μm (normal size 1–5 μm) in diameter, with vacuolization" (PMID: 37041648)
• Reduced platelet dense granules — electron microscopy shows decreased dense-granule number
• Impaired ATP secretion on lumiaggregometry
• Reduced platelet aggregation in response to ADP, collagen, and PAR1 (thrombin-receptor peptide), with normal response to arachidonic acid
• Impaired calcium mobilization and thrombus formation in functional assays (PMID: 37041648)
• Abnormal megakaryocyte maturation/accumulation in bone marrow in severe pediatric cases (PMID: 40521396)

Phenotype characteristics

• Onset: Lifelong/congenital — bleeding tendency present from an early age; some cases identified in childhood/adolescence (e.g., the 17-year-old proband), others diagnosed in adulthood after gynecologic or surgical bleeding.
• Severity: Variable — ranges from mild bruising/heavy menses to severe hemorrhagic syndromes in some patients (notably those with helicase-domain variants).
• Progression: Generally stable/chronic rather than progressive, though bleeding episodes are episodic (triggered by trauma, surgery, menstruation, childbirth).
• Penetrance: Incomplete in at least one reported kindred (asymptomatic carriers of the p.L589S variant), indicating that BDPLT20, unlike the classic AAA-domain-mutation families, may show variable expressivity/incomplete penetrance depending on variant location.

Quality of life impact

No disease-specific QOL instrument data were identified in the literature (no EQ-5D/SF-36 studies specific to BDPLT20 were found); qualitatively, recurrent menorrhagia, easy bruising, and bleeding after minor trauma or dental/surgical procedures are described as impacting daily life and requiring proactive hemostatic management (e.g., prophylactic interventions before procedures).

4. Genetic/Molecular Information

Causal Gene: SLFN14 (Schlafen family member 14), HGNC:32689, chromosome 17q12, OMIM *614958.

Variant spectrum (reported to date):

Variant classification: Reported variants are generally classified as pathogenic/likely pathogenic under ACMG/AMP criteria based on segregation with disease in affected families, absence/rarity in population databases (gnomAD), and functional evidence of protein dysfunction. ClinVar and ClinVar Miner catalog reported SLFN14 variants associated with this condition (ClinVar Miner).

Inheritance/transmission: Autosomal dominant, with three original families showing clear dominant segregation. Reduced/incomplete penetrance has since been documented in at least one family (helicase-domain variant), and maternal germline/gonosomal mosaicism has been reported as an unusual transmission mechanism (PMID: 36237120), which is clinically important for recurrence-risk counseling of "de novo"-appearing cases.

Functional consequences — gain vs. loss of function: The mechanism is complex and domain-dependent: - AAA-domain missense mutants (K218E, K219N, V220D) show dramatically reduced protein expression due to post-translational degradation from protein misfolding, and functional studies "propose a dominant-negative mechanism explaining heterozygous mutations in patients" (RNA 2018, PMID: 29678925). - A 2026 mechanistic study found that inherited-thrombocytopenia (IT)-linked mutations alter SLFN14 RNA substrate specificity rather than simply abolishing function: "IT-linked mutations alter SLFN14 RNA substrate specificity, enhancing depletion of type II tRNAs while reducing rRNA cleavage," triggering "ribosome stalling at codons decoded by type II tRNAs, stress signaling, and cell death" (PLoS Biol 2026, PMID: 42213791) — i.e., a neomorphic/altered-specificity mechanism rather than simple loss-of-function. - The T853fs helicase-domain frameshift shows markedly reduced SLFN14 protein expression in patient platelets, and — unlike AAA-domain mutants — "did not affect mitochondrial translation," instead disrupting "ion channels and dense granule" pathways (PMID: 40510593), indicating locus/domain-specific mechanistic heterogeneity.

Modifier genes: None specifically established; genetic background (species-specific, per mouse-model data below) appears to strongly modulate phenotype expression.

Somatic vs. germline: All reported cases are germline; no somatic SLFN14 thrombocytopenia has been reported (contrast with SLFN14's described antiviral/RNase roles in other contexts).

Allele frequency: Population database (gnomAD) frequency data specific to the pathogenic variants were not detailed in available search results; given the ultra-rare disease status and dominant-negative/gain-of-function-like mechanism, pathogenic alleles are expected to be essentially absent or present only as extreme rarities in gnomAD.

5. Environmental Information

No environmental risk factors, lifestyle factors, or infectious triggers are described as causal for BDPLT20 — it is a purely monogenic disorder. (Note: SLFN14 itself has been separately implicated in antiviral RNase activity against double-stranded RNA in unrelated contexts — "Human Schlafen 14 Cleavage of Short Double-Stranded RNAs Underpins its Antiviral Activity" — but this is a distinct biological role of the wild-type protein, not an environmental disease trigger for BDPLT20.)

6. Mechanism / Pathophysiology

Molecular function of SLFN14

SLFN14 is an RNA endoribonuclease that colocalizes with ribosomes and cleaves RNA — preferentially rRNA and ribosome-associated mRNA — leading to endoribonucleolytically mediated RNA degradation (RNA 2018, PMID: 29678925). A high-resolution cryo-EM structure (2025) revealed the SLFN14•RNA complex has "a medallion-like architecture" and that "metal-dependent acceptor stem cleavage requires the SLFN14 E-EhK motif," and structurally characterized "the environment of the SLFN14 disease hotspot at the RNA cleft entrance" (Nat Commun 2025, PMID: 40592880).

Causal chain (upstream → downstream)

1. Trigger: Heterozygous pathogenic SLFN14 variant (AAA-ATPase or helicase domain).
2. Molecular consequence: Altered/aberrant endoribonuclease substrate specificity and/or dominant-negative protein misfolding and degradation.
3. RNA-processing defect: In megakaryocytes and mature platelets, mutant SLFN14 drives rRNA and type II tRNA degradation, with disease variants showing enhanced tRNA cleavage and reduced rRNA cleavage relative to wild type (PMID: 42213791).
4. Ribosome/translation dysfunction: "SLFN14-defective platelets and mature MK showed signs of rRNA degradation; however, this was absent in undifferentiated imMKCL cells and granulocytes" — i.e., the defect manifests specifically during megakaryocyte maturation, not in progenitor/undifferentiated states (Blood 2023, PMID: 36790527). Ribosome stalling at codons decoded by depleted type II tRNAs triggers cellular stress signaling and cell death pathways.
5. Transcriptional dysregulation: Gene-expression analysis found "upregulated genes were enriched in pathways involved in (mitochondrial) translation and transcription," pointing to dysregulated mTORC1-coordinated ribosomal biogenesis as a downstream driver (PMID: 36790527).
6. Megakaryocyte-level consequences: Reduced megakaryocyte numbers in bone marrow (mouse model), abnormal mitochondria in megakaryocytes, dysregulated genes involved in ubiquitination, ATP activity, and cytoskeletal function (J Clin Invest 2025, PMID: 40794453).
7. Platelet-level consequences: Enlarged platelets (macrothrombocytes) with vacuolization, reduced number of dense granules, decreased ATP secretion, impaired aggregation to ADP/collagen/PAR1 (but preserved arachidonic acid response), impaired calcium mobilization, reduced platelet signaling to thrombin, and delayed thrombus formation.
8. Clinical outcome: Moderate-to-severe thrombocytopenia plus qualitative platelet secretion defect together produce the mucocutaneous bleeding phenotype.

Relevant ontology term suggestions

• GO (biological process): GO:0006364 (rRNA processing); GO:0034661 (ncRNA catabolic process); GO:0007596 (blood coagulation); GO:0030220 (platelet formation); GO:0007599 (hemostasis); GO:0032262 (positive regulation of ATP secretion, if bound)
• GO (molecular function): GO:0004521 (endoribonuclease activity); GO:0003924 (GTPase activity)/ATP-binding AAA domain function
• GO (cellular component): GO:0005840 (ribosome); GO:0031091 (platelet alpha granule); GO:0042629 (mast cell granule — analogous dense-granule terms); GO:0022626 (cytosolic ribosome)
• CL (cell types): CL:0000556 (megakaryocyte); CL:0000233 (platelet/thrombocyte)
• HP terms: listed in Section 3 above.

Cellular processes involved

Ribosome biogenesis/degradation, mitochondrial translation, megakaryocyte maturation and proliferation, platelet dense-granule biogenesis, ATP secretion, thrombus formation, and (in the mouse model) erythroid lineage commitment.

Molecular profiling data

• Transcriptomics: RNA-seq of patient platelets/megakaryocyte-like cells and mouse platelets/megakaryocytes show altered expression in translation, transcription, ubiquitination, ATP-activity, and cytoskeletal pathways (PMID: 36790527, PMID: 40794453).
• No dedicated proteomics, metabolomics, lipidomics, single-cell, or spatial transcriptomics datasets specific to BDPLT20 were identified in this search.

7. Anatomical Structures Affected

• Organ/system level: Primarily the hematopoietic/hemostatic system — bone marrow (megakaryopoiesis) and peripheral blood (platelets). Secondary manifestations occur wherever bleeding presents clinically: skin/subcutaneous tissue (bruising, hematoma), oral mucosa (gum bleeding), nasal mucosa (epistaxis), female reproductive tract (menorrhagia, postpartum hemorrhage), and skeletal muscle (spontaneous hematoma).
• Tissue/cell level: Megakaryocytes (bone marrow) and platelets (peripheral blood) — CL:0000556 and CL:0000233 respectively.
• Subcellular level: Ribosomes (GO:0005840), platelet dense granules (delta granules), mitochondria (abnormal mitochondrial morphology reported in mouse megakaryocytes).
• Localization/laterality: Systemic hemostatic disorder — not lateralized; bleeding can occur at any anatomic site subjected to trauma or physiologic stress (menstruation, delivery, surgery).

8. Temporal Development

• Onset: Congenital/lifelong — the underlying platelet defect is present from birth, though clinical bleeding may first become apparent in childhood, adolescence, or adulthood depending on exposure to hemostatic challenges (menarche, dental extraction, surgery, childbirth).
• Onset pattern: Chronic, with episodic (rather than acute single-event) bleeding manifestations.
• Progression: The underlying thrombocytopenia/platelet dysfunction is generally stable over time (not classically progressive), though bleeding episodes are triggered situationally.
• Disease course: Chronic, lifelong; no remission is described, as this is a structural/genetic platelet defect rather than an acquired, immune-mediated, or reversible process.
• Critical periods: Hemostatic challenge windows (surgery, dental procedures, menstruation, pregnancy/delivery) represent periods of elevated bleeding risk requiring proactive management.

9. Inheritance and Population

• Epidemiology: BDPLT20 is an ultra-rare disorder; no formal prevalence or incidence estimates (per 100,000) have been published. It has been identified in a modest number of families worldwide (originally 3 families/12 patients in the founding 2015 report, with additional single-family/single-patient reports subsequently from Italy, and other case reports through 2025), consistent with an inherited-thrombocytopenia subtype identified predominantly through next-generation sequencing referral cohorts (e.g., UK GAPP study, whole-exome-sequencing bleeding-diathesis diagnostic pipelines).
• Inheritance pattern: Autosomal dominant (OMIM: heterozygous mutation).
• Penetrance: Historically considered high/complete in the originally described AAA-domain-mutation families, but incomplete penetrance has since been reported for at least one helicase-domain variant (asymptomatic carrier mother and grandmother) (PMID: 40521396).
• Expressivity: Variable — bleeding severity ranges from mild bruising/menorrhagia to severe hemorrhagic syndrome; platelet count reduction and macrothrocytopenia severity also vary.
• Germline mosaicism: Documented in at least one family as "maternal gonosomal mosaicism" (PMID: 36237120) — clinically relevant since it can produce apparently sporadic/de novo cases with recurrence risk in future offspring.
• Founder effects / consanguinity: Not reported; families described span multiple ancestries (original US-derived and UK GAPP-ascertained families, an Italian family, and others), without an identified founder mutation or consanguinity requirement (consistent with autosomal dominant, not recessive, inheritance).
• Carrier frequency: Not established given the small number of known families and pathogenic-variant heterogeneity.
• Population demographics: No specific ethnic or geographic clustering has been reported; cases have been described in North American, European (UK, Italian), and other cohorts. Both males and females are affected, consistent with autosomal (non-X-linked) transmission, though several described probands are female (likely partly ascertainment bias via menorrhagia presentation).
• Age distribution: Diagnosed across a wide age range — from pediatric/adolescent (e.g., 17-year-old proband, pediatric twin brothers) to adult (31-year-old original proband and other adult family members across 3 generations in the founding family).

10. Diagnostics

Laboratory tests: - Complete blood count with peripheral smear — reveals thrombocytopenia and macrothrombocytes (enlarged platelets, occasionally giant forms). - Platelet aggregometry — reduced response to ADP, collagen, and PAR1 (thrombin-receptor-activating peptide); normal response to arachidonic acid. - Lumiaggregometry — decreased ATP secretion (dense-granule release defect). - Electron microscopy of platelets — reduced number of dense granules; vacuolization in some cases. - Bone marrow examination — may show megakaryocyte accumulation with arrested maturation in severe pediatric cases. - Flow cytometry-based "activation index" functional platelet assessment has been proposed as a newer diagnostic approach for inherited thrombocytopenias including macrothrombocytopenias (PMID: 40314328).

Genetic testing: - Recommended approach: Given the phenotypic overlap among inherited thrombocytopenias (>40 causal genes known), whole-exome sequencing (WES) is the diagnostic modality that has identified nearly all reported BDPLT20 cases, typically applied "at the end of the diagnostic trajectory" after standard hematologic workup fails to establish a diagnosis (PMID: 30431218). Targeted SLFN14 single-gene sequencing or an inherited-thrombocytopenia gene panel would also be appropriate once BDPLT20 is clinically suspected (thrombocytopenia + macrothrombocytes + secretion defect + dominant family history). - WGS, chromosomal microarray, karyotyping, and FISH are not first-line for this single-gene disorder but may be used to exclude syndromic/chromosomal causes of thrombocytopenia in the differential.

Clinical criteria / differential diagnosis: BDPLT20 should be distinguished from other inherited macrothrombocytopenias (e.g., MYH9-related disorders, Bernard-Soulier syndrome, ACTN1-related BDPLT15, gray platelet syndrome) and from other dense-granule secretion defects (e.g., Hermansky-Pudlak syndrome). The combination of dominant inheritance, moderate thrombocytopenia with macrothrombocytes, and a selective secretion defect with normal arachidonic-acid response is characteristic, but definitive diagnosis requires SLFN14 sequencing.

Screening: No population or newborn screening program exists given the disorder's rarity; diagnosis occurs via clinical ascertainment (bleeding history) followed by genetic confirmation, with cascade testing of at-risk relatives once a family-specific variant is identified.

11. Outcome/Prognosis

• No mortality data specific to BDPLT20 were identified; the disorder is not associated with a described reduction in life expectancy, and bleeding episodes, while sometimes severe, are generally manageable with hemostatic support.
• Morbidity: Chronic bleeding tendency affecting quality of life via recurrent bruising, menorrhagia, and bleeding after minor trauma or procedures; severe hemorrhagic syndrome has been reported in at least one adolescent case.
• Complications: Iron-deficiency anemia secondary to chronic menorrhagia is a plausible (though not explicitly quantified in available sources) complication; postpartum hemorrhage represents an important obstetric risk.
• Prognostic factors: Variant domain/location (AAA-ATPase vs. helicase) and degree of penetrance appear to modulate severity, though formal genotype-phenotype correlation studies with prognostic biomarkers have not been established.

12. Treatment

There is no disease-modifying or curative therapy for BDPLT20; management is supportive/symptomatic, following general principles for inherited platelet function disorders and thrombocytopenias:

• Antifibrinolytic therapy: Oral tranexamic acid has been used successfully for menorrhagia management in at least one adolescent patient (NCIT:C61129 Tranexamic Acid; treatment category: Pharmacotherapy, NCIT:C15986).
• Platelet transfusion: Prophylactic platelet transfusion is used to reduce spontaneous bleeding risk, generally following standard thresholds used for thrombocytopenia (e.g., ≤10×10⁹/L) or peri-procedurally to cover surgical/dental bleeding risk (NCIT term: Platelet Transfusion, NCIT:C15343 or similar transfusion-therapy term).
• DDAVP (desmopressin): Commonly used empirically in inherited platelet function disorders generally, though no BDPLT20-specific published trial or case data confirming efficacy were identified in this search — this should be considered plausible but unconfirmed for this specific gene defect.
• Supportive/procedural management: Peri-operative and peri-partum planning with hematology involvement, avoidance of antiplatelet/anticoagulant medications, and individualized bleeding-risk assessment.
• Experimental/investigational therapies: None specific to BDPLT20 are in clinical trials per available ClinicalTrials.gov search results; management remains empirical/symptomatic, consistent with the broader category of inherited platelet secretion disorders.

No gene therapy, cell therapy, or targeted molecular therapy has been developed or trialed for this condition to date.

13. Prevention

• Primary prevention: Not applicable in the traditional sense — genetic counseling and cascade testing of at-risk relatives (given autosomal dominant inheritance and documented germline mosaicism risk) is the principal preventive strategy for identifying at-risk family members before bleeding complications occur.
• Secondary prevention: Early genetic diagnosis in a proband enables surveillance and pre-emptive management (e.g., planning for menarche, surgery, pregnancy) in relatives found to carry the familial variant.
• Reproductive counseling: Given autosomal dominant transmission (50% risk to offspring of an affected individual) and at least one report of germline mosaicism (recurrence risk even when parental testing is negative), genetic counseling is important for family planning; prenatal or preimplantation genetic testing could theoretically be offered once a familial variant is known, though no specific literature on this practice for BDPLT20 was found.
• Behavioral/prophylactic measures: Avoidance of antiplatelet medications (aspirin, NSAIDs) and proactive hemostatic planning before invasive procedures.

14. Other Species / Natural Disease

• Taxonomy: Mus musculus (NCBITaxon:10090) is the principal model species used experimentally; no naturally occurring veterinary SLFN14-associated bleeding disorder has been reported (this is an experimentally engineered rather than naturally occurring animal disease).
• Orthologous gene: Mouse Slfn14 (murine ortholog of human SLFN14); the human p.K219N mutation corresponds to mouse p.K208N.
• Comparative biology — important species-specific divergence: Mouse and human phenotypes diverge substantially. The heterozygous K208N knock-in mouse shows "microcytic erythrocytosis, hemolytic anemia, splenomegaly, and abnormal thrombus formation," but notably "platelet function and morphology remain unchanged" in mice — contrasting sharply with the platelet-centric defects seen in human patients (Blood Adv 2021, PMID: 33496736). The homozygous K208N mutation is embryonic lethal in mice. This represents an important human-model mismatch: the global knock-in model better recapitulates an erythroid phenotype not classically described in human BDPLT20, while a separate platelet/megakaryocyte-specific conditional knockout (PF4-Cre-mediated deletion of Slfn14 exons 2–3) more faithfully reproduces the human platelet phenotype — "reduced platelet signaling to thrombin, reduced thrombin formation, increased bleeding tendency, and delayed thrombus formation," with reduced bone-marrow megakaryocyte numbers (J Clin Invest 2025, PMID: 40794453).
• Zoonotic potential: Not applicable; this is a non-infectious, purely genetic disorder.

15. Model Organisms

Model limitations: The global heterozygous knock-in mouse notably fails to recapitulate the platelet phenotype seen in humans (a clear human-model mismatch), while showing an erythroid phenotype not prominently described in human patients — underscoring that megakaryocyte/platelet-lineage-restricted conditional models are needed to faithfully model the human disease, and that cross-species extrapolation of SLFN14 biology must be done cautiously.

Applications: These models have been used to establish the RNA endoribonuclease mechanism, the megakaryocyte-maturation-stage specificity of the ribosomal/rRNA degradation defect, the dominant-negative/altered-substrate-specificity mechanism of disease variants, and thrombus-formation/bleeding phenotypes relevant to the human disorder.

Summary of Key Evidence-Anchored Claims

Sources: - OMIM #616913 — BLEEDING DISORDER, PLATELET-TYPE, 20; BDPLT20 - OMIM *614958 — SCHLAFEN FAMILY, MEMBER 14; SLFN14 - NCBI GTR: Platelet-type bleeding disorder 20 - MedGen C4310797 - ClinGen MONDO:0014830 curation - Orphanet: SLFN14-related thrombocytopenia - ClinVar Miner variants for Platelet-type bleeding disorder 20 - SLFN14 mutations underlie thrombocytopenia with excessive bleeding and platelet secretion defects (JCI 2015, PMID 26280575) - SLFN14-related thrombocytopenia: identification within a large series (Thromb Haemost 2016, PMID 26769223) - Role of the novel endoribonuclease SLFN14 in ribosomal degradation (RNA 2018, PMID 29678925) - Ribosome dysfunction underlies SLFN14-related thrombocytopenia (Blood 2023, PMID 36790527) - Novel SLFN14 mutation associated with macrothrombocytopenia (Orphanet J Rare Dis 2023, PMID 37041648) - Maternal gonosomal mosaicism in rare autosomal dominant SLFN14-related thrombocytopenia (Br J Haematol 2022, PMID 36237120) - Whole exome sequencing in the diagnostic workup of patients with a bleeding diathesis (Haemophilia 2019, PMID 30431218) - Molecular basis of inherited thrombocytopenias: an update (Curr Opin Hematol 2016, PMID 27438527) - Severe Thrombocytopenia Associated with a Genetic Variant in the Helicase Domain of SLFN14 (EJHaem 2025, PMID 40521396) - Novel mutation SLFN14 T853fs associated with inherited macrothrombocytopenia (Mol Ther Nucleic Acids 2025, PMID 40510593) - CryoEM structure of the SLFN14 endoribonuclease (Nat Commun 2025, PMID 40592880) - Type II tRNA cleavage by SLFN14 endoribonuclease variants drives global translational repression (PLoS Biol 2026, PMID 42213791) - Heterozygous mutation SLFN14 K208N in mice mediates species-specific differences (Blood Adv 2021, PMID 33496736) - Platelet-specific SLFN14 deletion causes macrothrombocytopenia and platelet dysfunction (J Clin Invest 2025, PMID 40794453) - A new approach to personalized assessment of functional platelet disorders in children (Blood Coagul Fibrinolysis 2025, PMID 40314328) - SLFN14 Gene - GeneCards

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• PMID:37041648: "heterogeneity in cell size, including giant forms over 10 μm (normal size 1–5 μm) in diameter, with vacuolization"
• closest text in source: "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"
• PMID:29678925 (abstract only): "propose a dominant-negative mechanism explaining heterozygous mutations in patients"
• closest text in source: "These findings could explain the dominant negative effect of heterozygous mutation on SLFN14 expression in patients' platelets"
• PMID:42213791: "ribosome stalling at codons decoded by type II tRNAs, stress signaling, and cell death"
• closest text in source: "This shift promotes ribosome stalling at codons decoded by type II tRNAs, triggering global translational arrest, stress signaling, and cell death"