P.M1304V: A NEW MUTATION IN THE A1 DOMAIN ASSOCIATED TO ATYPICAL VON WILLEBRAND 2B PHENOTYPE

WOODS AI; SáNCHEZ LUCEROS A; KEMPFER AC; BERMEJO EI; CALDERAZZO JC; GROSSO SH; MESCHENGIESER SS; LAZZARI MA

LIVERPOOL

Congreso; 58th Annual Meeting of the Scientific and Standardization Committee of the ISTH; 2012

INTERNATIONAL SOCIETY ON THROMBOSIS AND HAEMOSTASIS

Objectives: Atypical VWD2B was characterized by normal platelet count and VWF multimers, but positive ristocetin induced platelet aggregation (RIPA) at low doses. We describe a new mutation in heterozygosity, in association with atypical VWD2B in three members of a family with severe mucocutaneous bleeding symptoms.Atypical VWD2B was characterized by normal platelet count and VWF multimers, but positive ristocetin induced platelet aggregation (RIPA) at low doses. We describe a new mutation in heterozygosity, in association with atypical VWD2B in three members of a family with severe mucocutaneous bleeding symptoms. Methods: Bleeding score (BSS) (ISHT) was calculated in each patient. Bleeding time (BT Ivy), platelet count, FVIII:C, VWF:Ag, VWF:RCo, multimers, 1.2, 0.5 and 0.4 mg/mL RIPA, mixing tests to differentiate from pseudo-VWD. The exon 28 of the pts and 100 healthy donors was amplified (PCR) in fragments, and sequenced (ABI Prism 310). We designed primers avoiding pseudogen amplification.Bleeding score (BSS) (ISHT) was calculated in each patient. Bleeding time (BT Ivy), platelet count, FVIII:C, VWF:Ag, VWF:RCo, multimers, 1.2, 0.5 and 0.4 mg/mL RIPA, mixing tests to differentiate from pseudo-VWD. The exon 28 of the pts and 100 healthy donors was amplified (PCR) in fragments, and sequenced (ABI Prism 310). We designed primers avoiding pseudogen amplification. Results: Patient: boy (15-yrs old): BSS=5. BT>9 min; platelets=207,000/ìL; FVIII=70 IU/dL; VWF:Ag=17 IU/dL; VWF:RCo=15 IU/dL; VWF:RCo/VWF:Ag=0.88; Slight absence of high molecular weight multimers; 0.4 mg/mL RIPA positive. Post DDAVP 1h: BT>9min; platelets: 154,000/ìL; FVIII=130 IU/dL; VWF:Ag=59 IU/dL; VWF:RCo=40 IU/dL; VWF:RCo/VWF:Ag=0.68.: boy (15-yrs old): BSS=5. BT>9 min; platelets=207,000/ìL; FVIII=70 IU/dL; VWF:Ag=17 IU/dL; VWF:RCo=15 IU/dL; VWF:RCo/VWF:Ag=0.88; Slight absence of high molecular weight multimers; 0.4 mg/mL RIPA positive. Post DDAVP 1h: BT>9min; platelets: 154,000/ìL; FVIII=130 IU/dL; VWF:Ag=59 IU/dL; VWF:RCo=40 IU/dL; VWF:RCo/VWF:Ag=0.68. Mother (36–yrs old): BSS=5. BT=5.5min; FVIII=50 IU/dL; VWF:Ag=30 IU/dL; VWF:RCo=39 IU/dL; VWF:RCo/VWF:Ag=1.3; platelets=162,000/ul; 1.2 mg/mL 0.5 mg/mL RIPA: positive. Multimers: normal.(36–yrs old): BSS=5. BT=5.5min; FVIII=50 IU/dL; VWF:Ag=30 IU/dL; VWF:RCo=39 IU/dL; VWF:RCo/VWF:Ag=1.3; platelets=162,000/ul; 1.2 mg/mL 0.5 mg/mL RIPA: positive. Multimers: normal. Maternal aunt (25-yrs old): BSS=3. BT=7.5min; FVIII=40 IU/dL; VWF:Ag=26 IU/dL; VWF:RCo=26 IU/dL; VWF:RCo/VWF=1.0; platelets=205,000/ìL; 0.4 mg/mL RIPA: positive. Multimers: normal. In all patients mixing tests were compatible with VWD2B. We found in this family the heterozygous p.M1304V but not in donors. It was reported by us to the ISTH SSC VWF database. In silico analysis by using PolyPhen-2 (http://genetics.bwh.harvard.edu/pph2/) predicted the p.M1304V to be probably damaging with a score of 0.994 (sensitivity: 0.68; specificity: 0.97).(25-yrs old): BSS=3. BT=7.5min; FVIII=40 IU/dL; VWF:Ag=26 IU/dL; VWF:RCo=26 IU/dL; VWF:RCo/VWF=1.0; platelets=205,000/ìL; 0.4 mg/mL RIPA: positive. Multimers: normal. In all patients mixing tests were compatible with VWD2B. We found in this family the heterozygous p.M1304V but not in donors. It was reported by us to the ISTH SSC VWF database. In silico analysis by using PolyPhen-2 (http://genetics.bwh.harvard.edu/pph2/) predicted the p.M1304V to be probably damaging with a score of 0.994 (sensitivity: 0.68; specificity: 0.97). Conclusion: We described here a new missense substitution responsible for atypic VWD2B. Given that it was absent in the normal alleles and showed as probably damaging by Polyphen-2, we consider it is not a polymorphism.We described here a new missense substitution responsible for atypic VWD2B. Given that it was absent in the normal alleles and showed as probably damaging by Polyphen-2, we consider it is not a polymorphism.