UNUSUAL FINDING IN LABORATORY TESTS IN A PREGNANT PATIENT WITH VON WILLEBRAND DISEASE TYPE 2B

WOODS AI; SÁNCHEZ LUCEROS A; ALBERTO MF; KEMPFER AC; BLANCO AN; LAZZARI MA

KYOTO

Congreso; XXIII CONGRESS OF INTERNATIONAL SOCIETY ON THROMBOSIS AND HAEMOSTASIS; 2011

INTERNATIONAL SOCIETY ON THROMBOSIS AND HAEMOSTASIS

Type 2B von Willebrand disease (VWD2B) is characterized by enhanced ristocetin-induced platelet aggregation (RIPA). The abnormality of von Willebrand factor (VWF) may explain the bleeding tendency in these patients (pts): loss of high molecular weight multimers (HMWM), and thrombocytopenia. However, thrombocytopenia is not found in all the pts at baseline, but it impairs after stress conditions, such as pregnancy. In our group of 12 VWD2B pts (five females) two were pregnant. One of them, the only pt with basal VWF:RCo < 10 IU/dL, is a 27 year-old woman with bleeding symptoms (ISTH score = 6) in her 10th week of pregnancy, with Ivy BT > 9 min (nv < 4.5 min); FVIII = 56 IU/dL; VWF:Ag = 47 IU/dL; VWF:RCo < 10 IU/dL; VWF:CB = 6 IU/dL; VWF:RCo/VWF = 0.21; VWF:CB/VWF:Ag = 0.13; 150,000 platelets; RIPA positive 1.2 mg/mL, and absent 0.5 mg/mL. Multimeric profile: absence of HMWM. In the 26th week of pregnancy, laboratory tests were: Ivy BT = 7 min; FVIII = 90 IU/dL; VWF:Ag = 64 IU/dL; VWF:RCo = 23 IU/dL; VWF:RCo/VWF = 0.36; 114,000 platelets; RIPA positive 1.2, 0.5 and 0.4 mg/mL. Genetic studies: heterozygous 3922C>T (R1308C). Diagnosis: VWD2B. In the first laboratory control, it was surprising to find a VWF:RCo < 10 IU with positive 1.2 mg/mL RIPA, which is strongly suggestive of VWD2B. The R1308C mutation confirmed the diagnosis. The absence of 0.5 mg/mL RIPA in this first study could be related to VWF:RCo < 10 IU/dL. In the second study, the increase of VWF:RCo evidenced thrombocytopenia and a positive 0.5 and 0.4 mg/mL RIPA. Conclusion: According to these findings, a minimum level of VWF:RCo seemed to be required for 0.5 and 0.4 mg/mL RIPA positive. Faced with a laboratory testing in patients with VWF:RCo < 10 IU and positive 1.2 mg/mL RIPA, the diagnosis of VWD2B cannot be dismissed. In this case, the genetic study, the slight improvement of VWF:RCo and the thrombocytopenia given by the progression of the pregnancy in the patient were very important to confirm the initial diagnosis.