Prevalence of FVIII Inhibitors Among Children with Hemophilia A: Experience at the Jordanian Royal Medical Services

Replacement therapy is constantly required by Hemophilia A (HA) patients lacking coagulation factor VIII (FVIII). The most serious complication of this treatment is the development of neutralizing antibodies (inhibitors).The aim of this study is to determine the frequency of FVIII inhibitors among children treated for HA at the Jordanian Royal Medical Services.A total of 165 diagnosed HA patients receiving on-demand treatment, were tested for FVIII inhibitors between 2003 and 2018. The age range was 6 months to 16 years. Coagulation and inhibitor screening assays were performed, followed by Bethesda assay for inhibitor-positive samples to quantify FVIII inhibitor titers.Out of the 165 patients, 111 had severe hemophilia with FVIII level < 1%, 26 had moderate hemophilia with FVIII levels of 1-5% and 28 had mild hemophilia with FVIII levels of > 5%. Twenty patients had FVIII inhibitors, of whom 18 had high titers, 2 had low titers. The mean inhibitor level in low (titer) responders was 2.40 ± 0.85 BU, as opposed to 116.25 ±169.25 BU in high (titer) responders. In terms of disease severity, 18 of the 20 patients with FVIII inhibitors had severe HA, whereas two had moderate HA. No inhibitors were encountered in the mild HA group.Inhibitors only developed in moderate and severe cases of HA. The severity of the disease and age were the main contributing factors. The association between family history of inhibitors and the incidence of inhibitor formation warrants genetic evaluations to look for relevant mutations.