Case: Male, described as "a small child"; exact age not stated. Born at 26 weeks' gestation (extreme prematurity) by C-section for suspected placental abruption/preterm labor; perinatal course complicated by mild bronchopulmonary dysplasia and retinopathy of prematurity. DiseaseAssertion: Type 2B VWD, based on reduced VWF:RCo/Ag ratio (<0.7), absence of high- and intermediate-molecular-weight VWF multimers, and increased binding of patient VWF to formalin-fixed normal platelets at low ristocetin concentration (the gain-of-function assay that distinguishes Type 2B from Type 2A or platelet-type VWD). FamilyInfo: NA — no relatives' bleeding history or genotype reported for this patient. ParentalGenotype(s): NA (not tested/not reported) CasePresentingHPOs: HP:0001873 (Thrombocytopenia; platelet counts ranged 5,000-30,000/µL), HP:0012147 (Reduced quantity of VWF; VWF:Ag 54 then 26 IU/dL on repeat testing, nv 45-170 / 50-240), HP:0030129 (Impaired VWF:RCo; 24 then <10 IU/dL, nv >50 / 54-279), HP:0030132 (Absence of large VWF multimers — both high- and intermediate-weight multimers absent on electrophoresis) CaseHPOFreeText: Numerous purpura and petechiae on face, limbs, and trunk; easy bruising and bleeding from oral mucous membranes (no matching HPO code in the approved list); FVIII activity low-normal to reduced (63 then 27 IU/dL, nv 60-200 / 60-195); circulating platelet agglutinates seen on peripheral blood smear; bone marrow aspirate showed large platelet clumps and megakaryocyte nuclei surrounded by halos of clumped platelets — the paper's key finding, suggesting platelet agglutination occurs within the bone marrow itself, not only peripherally; increased binding of patient VWF to formalin-fixed normal platelets specifically at low ristocetin concentration (gain-of-function finding diagnostic for Type 2B, distinct from the reduced standard-dose VWF:RCo activity above). CaseNOTHPOs: NA CaseNOTHPOFreeText: No hepatosplenomegaly, no orthopedic abnormalities on exam; no schistocytes noted on peripheral smear (argues against a microangiopathic process). CasePreviousTesting: Targeted sequencing of VWF exon 28 specifically, clinically directed given the suspected Type 2B phenotype (Type 2B-causing mutations characteristically cluster in exon 28). Not genome-wide, not full VWF gene sequencing. GenotypingMethod: Gene sequencing of VWF exon 28 (specific sequencing platform not stated in the paper). PreviouslyPublished: PMID 15231945 (Christensen RD, Sola MC, Rimsza LM, et al. "Pseudothrombocytopenia in a preterm neonate." Pediatrics. 2004;114:273-275) — same patient, reported before the VWD diagnosis was established. Gene: VWF Variant: Heterozygous missense c.3923G>C, exon 28, p.Arg1308Pro. Same mutation previously reported in a different, unrelated family (Nurden et al. 2006, Blood, PMID 16720832) with abnormal megakaryocyte platelet release in CD34+ cell culture; this report extends that finding by showing the abnormality occurs in vivo in the bone marrow in a patient with this genotype. HGVS: NM_000552.5:c.3923G>C (p.Arg1308Pro). Paper states this directly ("G to C mutation at base 3923... arginine 1308 with proline"); also reports the older mature-protein numbering, R545P (offset of 763 residues, consistent with the length of the VWF signal peptide + propeptide). I independently corroborated the codon position: nt 3922-3924 = codon 1308, matching a real, independently confirmed ClinVar entry at the same codon for a different substitution (c.3922C>T, p.Arg1308Cys). ClinVarID: 100304 (VCV000100304.2) CAID: NA gnomAD: NA