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Twenty-two molecular diagnostic laboratories from 14 countries participated in a consortium study to estimate the impact of Factor VIII gene inversions in severe hemophilia A. A total of 2,093 patients with severe hemophilia A were studied; of those, 740 (35%) had a type 1 (distal) factor VIII inversion, and 140 (7%) showed a type 2 (proximal) inversion. In 25 cases, the molecular analysis showed additional abnormal or polymorphic patterns. Ninety-eight percent of 532 mothers of patients with inversions were carriers of the abnormal factor VIII gene; when only mothers of nonfamilial cases were studied, 9 de novo inversions in maternal germ cells were observed among 225 cases (approximately 1 de novo maternal origin of the inversion in 25 mothers of sporadic cases). When the maternal grandparental origin was examined, the inversions occurred de novo in male germ cells in 69 cases and female germ cells in 1 case. The presence of factor VIII inversions is not a major predisposing factor for the development of factor VIII inhibitors; however, slightly more patients with severe hemophilia A and factor VIII inversions develop inhibitors (130 of 642 [20%]) than patients with severe hemophilia A without inversions (131 of 821 [16%]).

We illustrate the usefulness of direct mutation detection for genetic counseling by showing its application to an extremely large mild haemophilia A pedigree (91 haemophiliacs) originating from the village of Aiani in Macedonia, northern Greece. The causative mutation has already been shown to be an A to T transversion in codon 280 of the FVIII gene which replaces Asn 280 (AAC) by Ile (ATC) and which creates a new Bam HI restriction site in exon 7. The latter permitted direct, rapid and reliable detection of the mutation in relevant family members. All major branches of the family were shown to share the mutation, and carrier status was diagnosed or excluded for 23 possible carriers. Other interesting characteristics of the Aiani haemophilic population are a slightly higher longevity and fecundity than that observed in the general population and a wide range of FVIII:C levels (5-25%) associated with the mutation.

Demographic data of the Greek haemophilia A and B population for the period 1972-1993 were analyzed. Prevalence at birth including known not-registered patients was calculated at 23.1 per 100,000 male births. However, the observed prevalence in 1993 was only 61% of the expected. Since 1975 the proportion of mild cases had significantly increased. Adjusted by age, severity and HIV status reproductive fitness of haemophiliacs was 0.62. Overall mortality was 2.6 times higher than in the general population, but 7.9 times among patients with severe haemophilia and 16.4 among HIV(+) haemophiliacs. Fifty out of 78 deaths occurred among HIV(+) patients and 28 of these were caused by AIDS. Inhibitor patients did not show excess mortality due to bleeding. Cancer mortality was equal to normal, but the number of deaths from ischaemic heart disease was 0.25 of the expected. Risk of death due to cerebral haemorrhage was 3.8 times higher in HIV(+) haemophiliacs than in HIV(-).