This study was conducted to evaluate the effect of an unaware carriership on the delay in diagnosis of haemophilia and the resulting effect of this delay on morbidity. Information on 73 haemophilia patients (<18 years) and their mothers was gathered from data of patients' medical records and completed by interviews with the parent(s). Although a positive family history was present in 52 gravidae, 16 of them (31%) were not aware of their carrier status at moment of delivery. Fifteen of these 16 unaware carriers, were carriers of a non-severe form of haemophilia. In mothers who were unaware of carriership for haemophilia instrumental delivery occurred more frequently than in mothers who knew they were carriers. This is disquieting since instrumental delivery poses a significant risk (relative risk: 17.8, 95% CI: 4.0-78.4) for intra- or extracranial bleedings in newborn haemophiliacs in comparison to spontaneous deliveries or caesarean sections. In 83% of the patients with a positive family history, diagnosis was established before the first bleeding episode. Patients diagnosed by bleedings presented more often with iatrogenic bleedings (38%) then patients who were diagnosed because of a positive family history (9%) (P < 0.05). In comparison to previous studies, more patients had a positive family history and in more haemophiliacs with a positive family history diagnosis was established before the first bleeding episode. Although this reflects the yield of improved diagnostic methods, further reduction of iatrogenic bleeding is possible by intensifying counselling of mild haemophilia carriers.

We evaluated inhibitor formation in a group of patients with mild haemophilia A caused by an Arg593 to Cys mutation. A remarkably high cumulative inhibitor incidence of 14% over 22 years was observed. Three of 49 patients developed transient, low-titre inhibitors, which remained below 2.0 BU mL(-1). Four patients with an Arg593 to Cys mutation developed high-titre inhibitors (>5.0 BU mL(-1)). Three of these patients have been described previously. In this study, we characterized inhibitory antibodies in a fourth patient with high-titre inhibitors. Epitope mapping studies revealed that antibodies were predominantly directed to the A2 domain of factor VIII. We addressed the role of human leucocyte antigen (HLA) class II alleles in inhibitor development in patients with an Arg593 to Cys mutation by HLA genotyping. In the group of inhibitor patients raised frequencies of HLA-DRB1*01 and HLA-DQB1*05 were observed that did not reached statistical significance. Our data suggest that inhibitor development in mild haemophilia A patients with an Arg593 to Cys mutation is not linked to HLA class II profile.

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