GENETIC-COUNSELING BY ANALYSIS OF INTRON-22 INVERSIONS OF THE FACTOR-VIII GENE

Ten patients with severe hemophilia A and 10 with moderate and mild he mophilia A were studied. Five of 10 unrelated patients with severe hem ophilia A had the distal telomeric int22h sequence, none had the proxi mal sequence, and one had a unique variant factor VIII gene rearrangem ent. Carrier detection was done in these six families. All mothers and two daughters of the patients were to be carriers. Six of the 15 at-r isk female relatives were heterozygous for the rearranged and normal a llele and were carriers. These results indicate that the rearrangement assay is very useful for carrier detection in families with severe he mophilia A.