Type 3 VWD and an inhibitor to VWF: Challenges in diagnosis

Developing an inhibitor to von Willebrand factor (VWF) is extremely uncommon. Consequently, patients with von Willebrand disease (VWD) tend not to be routinely evaluated for inhibitors, leading to the possibility of delay in inhibitor diagnosis. We present such an occurrence to raise awareness, with a view to avoiding such delays. A 1-year-old male with no family history of bleeding disorders or parental consanguinity presented with a tongue bleed lasting three days. Investigations confirmed a diagnosis of Type 3 VWD. Over the next few months, the patient received seven exposures to Humate-P (a plasma derived FVIII containing von Willebrand factor concentrate), but developed an anaphylactic reaction necessitating adrenalin and Benadryl (diphenhydramine). The reaction quickly abated and did not recur with further exposure to Humate-P. In 2013, due to recurrent epistaxis and tonsillar bleeding, the patient was commenced on prophylaxis receiving Humate-P 50 RCo U/kg twice weekly. Despite this regimen, he continued to experience recurrent epistaxis, leading to escalation of prophylaxis to 3/week. In November 2014, he showed persistent tonsillar bleeding, despite having received two doses of Humate-P (each 40 RCo U/kg) in the previous 12 hours. Testing revealed reduced VWF:Ag, VWF:RCo and FVIII:C recoveries. Further testing revealed an anti-VWF antibody (2.6 BU) of unspecified Ig type. Since diagnosis of the inhibitor, he has received 100 RCo U/kg daily for prophylaxis and immune tolerance. He is now bleed-free; however, monthly inhibitor testing shows that his inhibitor persists. Given the limited experience and literature on inhibitors in VWD, the prognosis for such cases is unknown.