<prompt> Christmas disease is due to deficiency of:September 2010Deficiency of factor IXDeficiency of factor XDeficiency of factor XIDeficiency of factor XII  <response>: Ans. A: Deficiency of factor IXHaemophilia B or hemophilia B is a blood clotting disorder caused by a mutation of the Factor IX gene, leading to a deficiency of Factor IX. It is the less common form of haemophilia, rarer than haemophilia A.It is sometimes called Christmas disease after Stephen Christmas, the first patient described with this disease 