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Severe haemophilia A in a female: a compound heterozygote with nonrandom X-inactivation

R A Seeler1, C L Vnencak-Jones, L M Bassett

  • 1Department of Paediatrics, Michael Reese Hospital and University of Illinois, Chicago, Illinois, USA.

Haemophilia : the Official Journal of the World Federation of Hemophilia
|December 3, 1999
PubMed

We report a case of severe haemophilia A (<1% factor VIII level) in a female resulting from an interesting and improbable combination of events. The patient inherited a factor VIII intron 22 inversion from her carrier mother, as well as a second factor VIII inversion involving intron 22 that arose de novo on her paternally derived X chromosome. In addition, the patient's paternally derived X chromosome had been preferentially inactivated in 95+% of her somatic cells. The patient's mother, who was clinically unaffected, carried an intron 22 inversion as well and also showed nonrandom X-inactivation. The patient's mother had a brother with severe haemophilia A. It is therefore likely that the mother's inversion was on her maternally derived X chromosome. Since she was unaffected, it is likely that her inversion-bearing X was the one that was preferentially inactivated.

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