SEVERE FACTOR-XI DEFICIENCY IN AN ARAB FAMILY ASSOCIATED WITH A NOVELMUTATION IN EXON-11

We investigated an 8-year-old Arab girl with severe factor XI deficien cy; one sibling and her father also have severe factor XI deficiency H er parents and her fathers parents are first cousins. Restriction anal ysis and DNA sequencing excluded the type I, II, III and TV mutations. We demonstrated a previously undescribed C --> A mutation at nucleoti de 1254 in exon 11 resulting in a threonine to asparagine (T --> N) su bstitution at amino acid 386. We postulate that this substitution inte rferes with folding and secretion of the molecule.