The Putative Factor IX Gene Promoter in Hemophilia B Leyden

is characterized by low levels of factor IX antigen and activity before the age of 1 5. whereas after puberty factor IX levels rise at a rate of about 5 % per year. A single base substitution (- A- ‘ T) at position-20 was identified in the putative promoter of the gene cloned from a patient with hemophilia B Leyden. This nucleotide change was confirmed in a second patient from the same F ACTOR IX (Christmas factor) is a vitamin K-depen-dent glycoprotein that plays a key role in the coagula-tion cascade. Genetic alterations in the factor IX gene that lead to impaired synthesis and/or aberrant molecules result in an X-linked recessive bleeding tendency (hemophilia B). As in normal patients, factor IX activity and antigen levels in hemophilia B patients (if measurable) remain constant throughout life, with only a small increase with age. ’